# A Brief History of Modern Philosophy/Book 1

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### FIRST BOOK the philosophy of the renaissanceFIRST BOOK the philosophy of the renaissance
##### A. The Discovery of the Natural ManA. The Discovery of the Natural Man

Burckhardt, in his famous treatise, Die Kultur der Renaissance in Italien, characterizes the Italian renaissance as the discovery of man. The historical conditions led to the emancipation of the individual. Man was no longer estimated from the mere viewpoint of his relationship to the Church or to his guild. He now became the subject of specialized interest and study. The discovery of ancient literature and art likewise contributed to this end. Man found a distinct form of culture outside the Church, with laws and ideals of its own. This expansion of the horizon furnished the opportunity for comparative study. In the north Protestantism, with its emphasis on personal experience and its insistence that civil life is independent of the Church, showed a similar tendency. In this way it became possible even here to develop both a theoretical and a practical interest in things which are purely human. Hence, both in the north and in the south, we find a number of interesting movements in the realm of the mental sciences during the period of the Renaissance.
1. Pietro Pomponazzi's little book, De immortalitate animæ (1515), may be regarded as an introduction to the philosophy of the Renaissance. Pomponazzi was born at Mantua in 1462, served with great distinction in the capacity of teacher of philosophy in Padua and Bologna, and died in the latter city in 1525. His friendship with ​Cardinal Bembo, who enjoyed the favor of Pope Leo X, saved him from persecution; but his book was burnt by the inquisition. His philosophic significance is due to his theory that the various forms and gradations of soul-life constitute a continuous natural series, and that ethics is self-explanatory. In opposition to the ecclesiastical Aristotelians he shows that the immortality of the soul is incapable of philosophic proof. Even in its highest forms soul-life is dependent on material conditions and its existence after the dissolution of the body cannot be demonstrated. There is no occasion moreover to criticize this conclusion on ethical grounds. On the contrary, man is obliged as well as capable of doing good without the hope of immortality; virtue is its own reward. This is the conclusion of the philosophy which is based on natural reason. But, according to Pomponazzi, the will may transcend reason: man can believe things which he is incapable of proving; faith proceeds from will, from personal impulse. By means of this separation between reason and will, between knowledge and faith, Pomponazzi conformed his theory with the authorized doctrines of the Church. He resorted to the same expedient in reconciling the reality of the human will with divine omnipotence. The Church rejected this distinction.
Nicolo da Machiavelli introduced the naturalistic method of investigation into politics and ethics in the same manner as Pomponazzi had revived the naturalistic psychology and ethics of genuine Aristotelianism. Descended from an old Florentine family (b. 1469), he entered the diplomatic service of the republican government of his native city which furnished him a splendid opportunity for studying men and affairs. After the fall of the Republic (1512) he joined the Medici, which brought him the ​profound contempt of his fellow citizens, who refused to accept his services after the republican government was again restored. He died in 1527.—Political interest made him a thinker. The misfortunes of Italy and its consequent conditions inspired him with a desire to restore its ancient spirit and power. Why should we imitate the splendid arts of the ancients and neglect their splendid deeds? But the sole possibility of accomplishing anything great requires us to press forward to the realization of great ideals without scruple! There are passages (especially in his Principe) in which Machiavelli seems to regard the ideal which a man proposes as an indifferent matter, if he only pursues it unscrupulously and energetically. But in the background of his thought there was constantly but a single ideal; the unity and the greatness of Italy. He regarded everything right which would contribute towards the realization of this ideal. Finding the Italians of his age lacking in a proper appreciation of greatness, he attributes it to the softening influence of the Church and of Christianity. In his Discorsi (Dissertations on the first ten books of Livy) he draws comparisons between the mind of antiquity and that of his own age, thus laying the foundation for a comparative ethics which was highly unfavorable to the modern period. Honor, magnanimity and physical prowess are not sufficiently appreciated now, and this is due to the fact that Christianity places the ideal of humanity in a transcendent world. To Machievelli it is perfectly clear that these attributes possess more than secondary value, they are intrinsically meritorious. Machiavelli reveals the true spirit of the Renaissance both by the purely human ideal which he presents to his fellow countrymen, as well as by his emulation of power for its own sake. ​The spirit of the Renaissance was likewise manifest in France. Michel de Montaigne (1533-1592), a French nobleman, spent his life in his private castle in the neighborhood of Bordeaux, far removed from the great movements agitating his age, devoting himself to literary pursuits. His interest in a purely naturalistic interpretation of human life, as he knew it from travel, books and above all from introspection, reveals his thoroughly modern spirit. At the beginning of his essays (which appeared 1580-1588) he remarks; je sus moy-mesme le sujet de mon livre. Closer study however reveals the fact that it is the way in which nature manifests itself in his own life that ready appeals to him. Nature, the great Mother of us all, reveals herself in a distinctively unique manner in every individual. Every human being has his forme maistresse, his ruling passion. It is this interest that accounts for Montaigne's own personal observations as well as for his thorough study of ancient literature. His enthusiasm for nature and his insight into the multiplicity of individual peculiarities cause him to revolt against all dogmatism, both the rationalistic and the theological. He opposes them both on the ground of the inexhaustible wealth of experience, which neither the faith of reason nor of dogma can satisfy. Our investigations constantly lead to the discovery of a greater number of differences and variations and thus increase the difficulty of reducing them to general laws. And we must remember, furthermore, that our knowledge of the objective world is through sense perception, and that the sense organs as a matter of fact only reveal their own state, not the real nature of objects. And finally, if we attempt to form a conception of Deity, we imagine Him in human form, just as animals would conceive Him in ​animal form, and we presume that this whole universe was created and is preserved for the welfare of man alone.—But Montaigne is not a sceptic. There are two fundamental ideas, vitally related to each other, to which he firmly holds, viz. the idea of the variety of individual peculiarities, and the idea of the eternity of nature revealing itself in every natural event.
Luis Vives (born in Valencia 1492, died in Brügge 1542), a Spanish scholar, whose contributions to philology and pedagogy have likewise been of great importance, became the forerunner of modern empirical psychology through his book De anima vita (1538). He insists that experience must be the foundation of all knowledge and, true to this principle, he holds that our chief concern is not to know what the soul is, but to know how it acts. He therefore undertakes to emancipate psychology from metaphysics and theology. He follows the descriptive rather than the analytic and explanatory method. His description of the various psychical phenomena, especially of the emotions, still retains its interest. He regards the soul and the vital principle as identical, and he constantly seeks to combine physiology, as he understands it from the works of Galen, with his psychology. He holds however that, whilst the souls of plants and of animals (the principle of organic life and of sensory experience) evolve from matter, God creates the human soul. The proof of the divine origin of the soul consists of the fact that man is never satisfied with the sensible and finite, but is forever striving to realize the infinite.
Two years after the appearance of Vives' work, Philip Melanchthon (1495-1560), the reformer and "Preceptor of Germany," published his Liber de anima, a book which made a profound impression upon Protestantism. He ​follows Aristotle and theology more closely than Vives and his book is therefore of less importance for the history of psychology than that of Vives. Melanchthon's mild conception of human nature, contrasting sharply with that of Luther and the Lutheran zealots, had a wholesome influence however. His theory of the "natural light" shows this clearly: there are a number of ideas implanted in us by God, hence innate (notitiæ nobiscum nascentes), and these form the basis of all thought and of all value-judgments. This "natural light" was darkened by the Fall which necessitated the giving of the law at Sinai. The content of the ten commandments however is the same as the "natural light." It follows therefore that ethics may be founded on human nature (naturalistically). But it is powerless to quicken the life of the spirit and give peace. (Philosophiæ moralis epitome.)
The doctrine of the natural light was taken up enthusiastically by the Reformed provinces and applied most rigorously, especially with reference to the idea of authority and of the state. John Althaus (Althusius, 1557-1638), the Burgomaster of Emden, made this theory the basis of his idea of popular sovereignty in his Politica methodice digesta (1603). Even before him, Jean Bodin (in La republique, 1577) had conceived and elaborated the idea that sovereignty is indivisible and can exist in but a single place in the state. Althaus now teaches that it always belongs to the people. Rulers come and go, but the people constitute the permanent foundation of the state. They are the source of all authority because it is their welfare that constitutes the cause and purpose of the existence of the state. As a matter of history the sovereignty of the people is revealed in the first place by the fact that in most states there are a number of officers ​exercising governmental control by virtue of their appointment by the people, and, in the second place, by the fact that the people terminate the government of tyrannical princes by revolution. From the viewpoint of philosophy, on the other hand, the theory of popular sovereignty is demonstrated by the fact that either an expressed or tacit contract (pacturn expressurn vel taciturn) underlies the origin and perpetuity of the state; it is by virtue of such contract that the people institute organized society and submit themselves to governmental authority. Athaus therefore maintains that the purpose of this contract can be nothing else than the welfare of the people. He seems to construe this contract more in the form of a directive idea than as an historic fact. The state is simply the most comprehensive community; its antecedents being the narrower circles of the family, the neighborhood and the corporation.
The appearance of Hugo Grotius’ De Jure belli et pacis (1625) marks an epoch in the sphere of jurisprudence and political theory. Born at Delft in 1583, his great learning in the field of jurisprudence and of theology attracted attention early in life. Politically he belonged to the aristocratic and liberal theological party of Oberbarnevelt. He was rescued from the imprisonment into which he was cast after the fall of Oberbarnevelt by his wife's cunning. Thereafter he lived in Paris, and finally received the appointment of ambassador to Sweden (1645). Grotius makes war his starting point and requires how it may be abolished. There are four kinds of war between states— between an individual and the state—between different individuals—between the state and the individual. 1. When states declare war they have no right to abrogate the rights of the individual and the obligations of humanity. ​War must be conducted for the sake of peace, and hence not in such a way as to make peace impossible. It is through this principle that Grotius became the founder of the modern theory of popular sovereignty. 2. When the individual declares war against the state it is an act of rebellion, and, in evident opposition to Althaus, Grotius denies the right of the people to revolt. 3. War between individuals, in a well-regulated state, is limited to justifiable self-defense. 4. War of the state against the individual takes the form of punishment. The state's right to punish must not be construed as the right of expiation. Punishment is justified only in case the pain imposed on the individual contains the possibility of greater good both to the individual himself and to the community.—In all of these various contingencies the authority of the law is independent of theological grounds. It proceeds from human nature (ex principiis homini internis). Human beings congregate and are led to organize societies under the influence of a native social impulse (appetitus societatis); but the constitution of society presupposes certain principles of government—above all the inviolability of every promise—and the people therefore pledge themselves to the observance of these rules either by expressed or tacit contract. The obligation to keep promises, according to Grotius, rests upon a primitive promise. In direct opposition to Althaus, Grotius holds that the people—i. e. after they have constituted society on the basis of the primitive contract—can renounce its sovereignty absolutely because it confers it on a prince or corporation. His theory of the relation of the state to religion, on the other hand, is more liberal than that of the strictly confessional Althaus: The only requirement which the state can make ​of its subjects is the acceptance of general religious ideas (the unity of Deity, predestination).
3. The general religious ideas which Grotius has in mind, and which even Melanchthon accepted, were elaborated by a series of thinkers in more or less direct opposition to the confessional conception. Similar ideas had already been expressed during the period of the older Italian Renaissance (especially in the Platonic Academy at Florence). Jean Bodin (a Frenchman learned in law, d. 1596), previously mentioned, in his remarkable work called the Dialogue of Seven Men (Colloquium Heptaplomeres) describes a conversation between men whose religious viewpoints were widely at variance. Two of the men, defending natural religion—one of them dogmatically, the other more critically—engage in controversy with a Catholic, a Lutheran, a Calvinist, a Jew, and a Mohammedan. According to Bodin, true religion consists in the purified soul turning to God, the infinite essence. This religion can be exercised within any of the various religions, and the seven men therefore separate in charity and peace.
Bodin’s book was in circulation for a long time in nothing but manuscript copies. In 1624, however, the English diplomat, Herbert of Cherbury, published his book De veritate, which remained the text book of natural religion for a long number of years. Cherbury takes issue with those on the one hand who regard confessional faith as superior to rational knowledge, and seek to inculcate such faith by threats of future punishment, and those on the other hand who pretend to depend wholly on the rational understanding, together with those who would derive everything from sense experience, conceiving the soul as a blank tablet (tabula Rasa). He holds that there ​is an immediate, instinctive sense which guides all men to the acceptance of certain truths (notitiæ communes). This sense is the natural product of the instinct of self-preservation, which is another instance of the operation of divine predestination. The following propositions are instinctive truths of this order: Two contradictory propositions cannot both he true; There is a first cause of all things; No one should do anything towards another which he would be unwilling to suffer in return. According to Cherbury, even natural religion rests on an instinctive foundation, an inner revelation experienced by every human soul. The evidences of this revelation consist of the fact that we have capacities and impulses which finite objects fail to satisfy. The following five propositions contain the essence of all religion: There is a Supreme Being; This Being must be worshipped; The truest worship consists of virtuous living and a pious disposition; Atonement for sin must be made by penitence; There are rewards and punishments after the present life. Questions which go beyond these five propositions need give us no concern.
Jacob Böhme (1575-1624), the Gorlitz cobbler, and the profoundest religious thinker of this period, does not intend to oppose positive religion, as is the case with Bodin and Cherbury. He means to be a good Lutheran. He simply wishes to furnish a philosophy which will harmonize with Protestantism. Although a mere artisan, the influence of mysticism and natural science gave rise to grave doubts in Böhme’s mind. He accepted the Copernican astronomy. He could no longer regard the earth as the center of the universe. But must it not follow therefore that man is but a negligible quantity in the universe, and is it not true that the great world ​processes must take their course regardless of the fate of man? Notwithstanding all this, if we should still presume to maintain our faith in God as the author of the universe, what shall we say in explanation of the evil, strife and suffering which everywhere abounds? After profound spiritual struggles Böhme discovered answers to these questions which he published in his Morgenröte im Aufgang (1612). His thought moves in majestic symbols drawn from the Bible and the chemistry or alchemy of his time. He is however fully aware that these symbols can express the pure thought relations but very imperfectly. He was also well aware of the fact that his ideas went beyond the theology of the church. But he stoutly denied the charge that his ideas were heathen. “I write like a philosopher, not like a heathen!” He meets the first doubt with the idea of the presence of God’s power and nature in everything—in the human body as well as in the stellar spheres, and the latter must therefore be possessed of a kind of life—in human souls and throughout infinite space. As a matter of fact our bodies reveal the same elements as are found in the other objects of nature. In objective nature the divine activity is veiled; but in the mind of man it is clearly conscious. It follows therefore that we possess what is highest within ourselves and there is no need that we should seek it beyond the stars. He solves the second doubt with the idea that man must assume an original multiplicity within the divine unity, on the ground that multiplicity cannot be derived from unity, and moreover because opposition and difference are necessary conditions of consciousness: “A being incapable of experiencing contrasts could never become conscious of its own existence.” But multiplicity and contrast furnish the possibility of disharmony, ​of strife and evil. The origin of evil is explained by the fact that a single element of Deity strives to become the whole Deity. This accounts for the profound conflict and the intense suffering in the world through which man and nature are to fight their way through to peace. In this conflict God is not far off: it is indeed his own inner conflict. “Everyone whose heart is filled with love and who leads a compassionate and sweet tempered life, fighting against evil and pressing through the wrath of God into the light, lives with God and is of one mind with God. God requires no other service.”
4. The effort to attain a natural, purely humanistic conception likewise affected the logic of the Renaissance, as well as the psychology, ethics and philosophy of religion. The scholastic logic, by which is meant the logic of the middle ages, was primarily the servant of theology and of jurisprudence; it was adapted to the single purpose of drawing valid conclusions from the presuppositions established by authority. But an effort was now being made to discover the relation which exists between logical rules and natural, spontaneous, informal thought. It was with this end in view that Pierre de la Ramee (Petrus Ramus) attacked the Aristotelian logic (Institutiones Logiciæ, 1554, French Ed. 1555). He was the son of a charcoal burner (born in northern France 1515), and it was by sheer dint of his thirst for knowledge and his indefatigable energy that he forged to the front and enjoyed a most successful career as a teacher in the College of France. Being a Protestant, he fell a victim to the massacre of St. Bartholomew’s night (1572). Ramus called attention to the fact that the earliest philosophers had no formal logic, and that the spontaneous functions of thought are not confined to these men, but that they ​can be studied in the mathematicians, the statesmen, the orators, and the poets as well. These observations however still failed to lead Ramus to the founding of a psychology of thought. As a Humanist, he rejoices in the fact that the classical authors could be of service to logic. His own treatment however does not get much beyond the theory of inference, in which he differs but little from Aristotle. A controversy between the Ramists and the Scholastics arose at this time—enlisting France, England, Germany and the North—which contributed greatly to the development of freedom of thought.
Franz Sanchez (1562-1632), a Spaniard, professor of medicine and philosophy at Montpelier and Toulouse, felt the need of substituting a new method for the scholastic logic. He expresses his dissatisfaction with the existing state of knowledge in his book Quod nihil scitur (1581). The further he presses his investigations the greater are the number of difficulties which he finds. Owing to the mutual interdependence of all things, and the infinitude of the universe, he has but little hope of attaining certainty in knowledge. He insists on observation and experiment however, and takes as his motto; Go to the facts themselves. But the ultimate ground of certainty is nevertheless within the human mind itself: no external knowledge can equal the certainty which I have of my own states and actions. On the other hand however this immediate certainty of inner experience is far inferior to the knowledge of external objects in point of clearness and precision.
Bacon’s enthusiastic optimism concerning the future prospects of science presents a sharp contrast to the pessimism of Sanchez. He hoped for great things and devised magnificent plans. He anticipated great ​advancement in culture which was to be brought about by the mastery of the forces of nature through the aid of natural science, a study which ancient and mediæval thinkers had contemned. The aim and purpose of science is the enrichment of human life by means of new discoveries. Bacon nevertheless bestows high praise on the love of contemplation (contemplatio rerum): the vision of light is far more glorious than all the various uses of light. These sublime hopes furnish an insight into Bacon’s personal character and his method of doing things. He justified the use of every available means in acquiring the conditions without which he thought his scientific plans impossible, on the plea of their necessity to the realization of his great purposes.
Francis Bacon of Verulam was born of an excellent family in 1561. In order to acquire the influence and the wealth which he regarded as necessary to his purposes, he threw himself into politics and gradually rose to prominent positions; finally attaining to the office of Lord Chancellor. But he gained this promotion by dishonorable compromises with the despotic caprice of Elizabeth and James the First. Under the charge of bribery and the violation of the law, parliament deposed him in 1621. His last years were spent in retirement engaged in scientific pursuits. He died in 1626. His political activities had not prevented him from continuing his studies and the production of important works. The tragedy of his life consisted in the fact that ulterior demands claimed his attention to so great an extent that not only his real purpose but even his personal character had to suffer under it.
Bacon describes himself as a herald (buccinator) who announces the approach of the new era without ​participating in it himself. He insists on quitting fruitless speculation and introducing the method of experience, induction, in every department of knowledge,—in the mental sciences as well as in the natural sciences. In the Novum Organon (1620) he examines the reasons why the sciences are inadequate and describes the inductive method. In the De Dignitate et Augmentis Scientiarum (1623) he presents a sketch of the actual state of the sciences and proceeds to show, frequently in a most brilliant manner, the gaps which still remain to be filled.
If a man would understand nature correctly, he must first of all reduce himself to a blank tablet. No one can enter the kingdom of nature except as a little child. But we are all hindered to a greater or less degree by various illusions, both native and acquired (Idola mentis). These may be divided into four classes. The first class, having its origin in human nature, is common to all mankind (Idola tribus). This is why we are constantly disposed to regard things from the viewpoint of their relation and their similarity to ourselves, rather than from the viewpoint of their true place in the general order of the universe—ex analogia hominis instead of ex analogia universi. We assume a greater degree of order and simplicity in things than the facts justify. We discover teleologic causes in nature because our own actions reveal such causes. The second class rests on individual peculiarity (Idola specus; every one interprets nature from the viewpoint of his own cave). This accounts for the fact that some minds are more impressed by the differences of things, whilst others are disposed to emphasize their resemblances. Some are constantly striving to analyze and reduce things to their elements; others are engrossed with ​totalities. The third class is due to the influence of language upon thought (Idola fori). The formulation of words is governed by the needs of practical life, but exact thought frequently requires distinctions and combinations which differ widely from those of common speech. In certain cases there is a superabundance of words, in others there are too few. The fourth class (Idola theatri) is ascribed to the influence of traditional theories.
We must get rid of all these illusions. Bacon makes no attempt to show how this may be accomplished. The conception of the idola tribus contains a profound problem which Bacon failed to see, a problem however which acquired vast importance at a later period; we are obliged in every case to interpret reality from the human standpoint (ex analogia hominis); but in that case the question arises as to how our knowledge of the world can possess objective validity.
Bacon takes exception to the prevalent method of induction on the ground of its being limited to positive cases (as an induction per enumerationem simplicem). He insists that we must likewise take note of results in cases where the phenomenon under consideration is absent. He demands furthermore that we investigate the modifications of phenomena under varying conditions. After sufficient material has been gathered by these methods—and in order to avoid being overwhelmed by the confused mass of facts (for, citius emergit veritas ex errore quam ex confusione)—it is necessary to formulate a tentative hypothesis and examine the cases which seem to establish or refute the hypothesis. Bacon’s method is therefore not a pure induction. He has a presentiment of the profound mutual dependence of induction and deduction. ​His depreciation of the quantitative method however prevents him from attaining the true method of natural science as we find it in his contemporaries, Kepler and Galileo.
According to Bacon, the method of induction gives us an insight into the “Forms” of things. The Baconian “Forms,” from one point of view, bear a close resemblance to the Platonic ideas, and from another they are analogous to the laws of natural science. The latter conception he frequently emphasizes very strongly. He says, e.g. “If the Forms are not regarded as principles of activity, they are nothing more than fictions of the human mind.” Generally speaking, Bacon occupies a unique position in the transition from the ancient and scholastic world view to that of the modern period. This is clearly manifest in his effort to acquire a mechanical theory of nature. We never understand an object until we are in position to explain its origin, and the genetic processes of nature are brought about by means of minute variations (per minima) which elude our senses. But science uncovers the secret process (latens processus) and thus reveals the inherent relation and continuity of events. We do not discover, e.g. that the “Form” of heat is motion through! sense perception; nor do the senses reveal the fact that the sum total of matter remains constant throughout all the changes of nature.
Bacon makes a sharp distinction between science and religion. The former rests upon sense perception, the latter upon supernatural inspiration. In philosophy the first principles must be submitted to the test of induction; in religion, on the other hand, the first principles are established by authority. Reverence towards God increases in direct proportion to the absurdity and ​incredibility of the divine mysteries accepted. Bacon however believes in the possibility of a purely natural theology. The very uniformity of natural causation reveals the existence of deity.
In ethics Bacon makes a distinction between the theory of the moral idea (de exemplari) and the theory of the development of the will (de cultura anima). The former he finds thoroughly elaborated by the ancients; but the latter has received but very little attention hitherto.

##### B. The New Conception of the WorldB. The New Conception of the World

The middle ages developed its theory of nature as well as that of the spiritual life on the foundation of Greek antiquity—except where its ideas were derived from the Bible and Christian tradition.—They received their theory of medicine from Galen, their astronomy from Ptolemy, their philosophy from Aristotle. Their world view was a combination of the theories of Aristotle and Ptolemy with the Biblical doctrines: the earth is stationary and forms the center of the universe; the sun, moon, planets and the fixed stars, attached to firm but transparent spheres, revolve around it. The sub-lunar world, i.e. the earth and the space intervening between the earth and the moon, is the realm of change and death. Here the four elements (Earth, Water, Air, Fire) are in a state of constant motion. Each seeks its “natural place.” Weight consists of the natural tendency to descend, lightness consists of the tendency to ascend. Beyond this moon-sphere is the realm of ether, consisting of matter which has no “natural place,” which is therefore capable of continuing its motion eternally with absolute regularity. The motions of the heavenly bodies—due to this absolute regularity—are a direct copy of the nature ​of Deity. They move in circles because the circle is the most perfect figure; it invariably returns into itself! The universe is bounded by the sphere of the fixed stars which is moved by the Deity himself, whilst the lower spheres are moved by various ethereal spirits.
This world theory seemed to be in harmony with the authorities of the age, Aristotle and the Bible, and at the same time to be in accord with the direct evidence of sense perception. This is why it required such a severe struggle to supplant it. It not only required the repudiation of venerable authorities, but even the most familiar sensory impressions. It was this profound revolution that constituted the stupendous task of the great Copernicus. The epistemological foundations of the ancient world view were unsettled by two men who had no acquaintance with its doctrine.
1. Nicholas Cusanus (1401-1464), a profound thinker with Neoplatonic and mystical tendencies, had even in the fifteenth century gone beyond the traditional view of a limited and stationary universe. Born in Cues (near Trier), he was educated by the “Brothers of the Common Life.” He afterwards continued his studies in Italy. He attained to high ecclesiastical positions and his philosophy has its starting point in theological speculations. In his doctrine of the Trinity he regards the Spirit as the uniting principle which combines the oppositions implied in the characters of Father and Son; spiritus sanctus est nexus infinitus. He afterwards discovers analogous principles in human knowledge and in nature generally.—Falckenberg’s Grundzüge der Philosophie des Nicholas Cusanus (Breslau, 1880) and M. Jacobi’s Das Weltegebaude des Kardinals Nicholas von Cues (1904) are splendid memoirs of this remarkable man. ​All knowledge consists of a process of combination and assimilation. Even sense perception combines various impressions into unitary wholes and these are in turn reduced to ideas and the ideas finally to concepts. In this way the intellect (intelligentia) is forever striving for unity—but it invariably requires an antithesis, something “other than” (alteritas) itself to effect its development. Finally, in order to transcend the antitheses, thought undertakes to conceive them as the extremes of a continuous series. In this way maximum and minimum are united by a continuous series of magnitudes. But we are unable to reconcile all antitheses: thought culminates in antitheses, i.e. there always remains an unassimilated increment beyond itself. It is as impossible for our thought to comprehend the Absolute as it is to describe a circle of pure polygons, even though we may constantly approach it more closely. Although we are incapable of conceiving the Absolute, Deity, we nevertheless understand (such is the nature of the intellect) our incapacity, and the ignorance in which our thought culminates, as a matter of fact, is a scientific ignorance (docta ignorantia). (One of the most interesting of the works of Cusanus is entitled De docta ignorantia.)
This fundamental peculiarity of our knowledge is likewise of importance in the study of nature. We are constantly striving to form continuous series from given points, but without being able to arrive anywhere. Thus, e.g. we can divide our idea of matter to infinity, in experience we must always be satisfied with a finite division, and the atom concept therefore always remains relative. It is the same with the idea of motion: an everlasting, perpetual motion were only possible in case there were no resistance. Here Cusanus anticipates the principle of ​inertia. And the same thing applies even to the determinations of locality: we always regard the objects of the universe from a given place which is, for the time being, the center of the universe for us; the universe as such, however, can have neither center nor circumference, and all motion is relative. The theory that the earth is at the center of the universe is therefore false. However if it is not at the center of the universe, it cannot be at rest; it must be in motion even though we do not perceive it. There is no ground therefore for the assumption that the processes of origin and decay should be confined to the sublunar sphere; we must rather assume that all world bodies are subject to similar conditions to those of the earth. According to Cusanus, therefore, the same principle which precludes our knowledge of Deity likewise demonstrates that the world can neither be limited nor stationary as was hitherto believed.
2. It was characteristic of the ancient, aesthetic conception of nature to emphasize the opposition of Form and Matter. The “Forms” of natural phenomena likewise contained their explanation. Bernardino Telesius (1508-1588) introduces the concept of Force (principium agens) instead of Form (in his work De rerum natura, 1565-1587), as the opposite of Matter. He believes that this conforms more closely with the facts of experience. The “Forms” were mere qualities, which explain nothing. He rejected the traditional theory of the “natural places” and the qualitative distinction of the elements. There are as a matter of fact but two fundamental forces; the one expands (heat), the other contracts (cold), and the various “Forms” which Matter, in itself unchanging and quantitatively constant, assumes must find their explanation by reference to the interaction of these two ​forces. There are no “natural places,” for space is everywhere the same. Different places in space do not of themselves involve any qualitative differences.
Telesius was born at Cosenza in the vicinity of Naples. His circumstances were sufficiently comfortable to provide him the opportunity to devote himself to science. He taught in the University of Naples and founded an Academy in his native city. He had planned to substitute a new theory, based on experience, for Aristotelian Scholasticism. But his critical equipment was inadequate to the accomplishment of this ideal. His general principles however mark an important advance. The details of his natural philosophy are no longer of interest. But his ideas on the psychology of knowledge still continue to be of considerable importance. He tries to bring thought and sensation into the closest possible relation. Should an object which has once been perceived in the totality of its parts and attributes recur at some later time with certain of its parts and attributes lacking, we can supply the parts which are lacking and imagine the object as a totality notwithstanding the fact that we perceive it but in part. We can imagine fire, e.g. with all its attributes, even though we only see its light, without perceiving its heat and its consuming energy. Intellection (intellegere) is the process of construing our fragmentary experience into such a totality. Even the highest and most perfect knowledge simply consists of the ability to discover the unknown attributes and conditions of phenomena by means of their similarity to other cases known as a totality. Inference simply means the recognition of the absent attributes by this method. The simplest sensory impressions are therefore related through a large number of intervening degrees to the highest ​product of scientific thought, and there is no ground for attempting to deduce our knowledge from two different sources or faculties. The problem as to whether similarity is a sensory quality like color and tone remains unsolved, as even Patrizzi, a contemporary of Telesius, charged against him.
Telesius is inclined to ascribe sensitivity to all matter, just as, on the other hand, he regards the soul as material (with this exception, he postulated a supernatural part in the soul on theological grounds which he regarded as a forma superaddita). Every human soul, like everything else, possesses a native impulse towards self-preservation, which constitutes the foundation of ethics. Human virtues represent the various attributes which are favorable to the preservation of the individual. Wisdom is an indispensable condition which must therefore cooperate with all the other virtues (as virtus universalis). The social virtues, which are comprehended under the concept humanitas, are of great importance, because intimate association with others is a necessary condition of self-preservation. The climax of all virtue however is magnanimity (sublimitas), which finds its sufficient satisfaction in its own personal integrity and diligence. Telesius conceived his ethics in the spirit of the Renaissance, and it produced a lasting impression. His natural philosophy and his psychology were likewise very influential, especially over Bacon and Bruno.
3. Nicholas Copernicus (Coppernick), the founder of the modern theory of the universe, was born at Thorn (1473), studied at Cracow and at various Italian Universities and was prebendary at Frauenburg, partly as Administrator, devoting part of his time to his studies. He took no part in the great controversies agitating his ​age. But he seems to have had a measure of sympathy with the religious movement, and he fell into discredit during his latter years on account of his liberal, humanistic tendency. He began the elaboration of his astronomical theory already in 1506, but he was hesitant about its publication, and the first printed copy of his work De revolutionibus orbium coelestium only appeared shortly before his death (1543). The matter which specially concerns us is the epistemological presuppositions which form the basis of this work. Two of its presuppositions must claim our attention.
Nature always takes the simplest course. The theory of the whole universe revolving around so small a body as the earth is inconsistent with this principle. And the case is similar with the theory that the planetary orbits should not be simple circles but a very complicated system of epicycles. On the other hand, if we regard the sun as the center of the universe, and the earth and the planets as revolving around it, we have a very simple theory of the universe.
The second presupposition is the principle of the relativity of motion previously suggested by Cusanus. The perception of motion is not adequately explained by the mere reference to the fact that a perceived object has really changed its position in space. It may likewise be due to the fact that the perceiving subject has moved. If we therefore assume that the earth, from which we observe the motion of the heavenly bodies, is itself in motion (around its axis and around the sun), we will be in position to explain the phenomenon quite as well (only more simply) as the traditional theory.
Copernicus still adhered to the idea of a finite universe and regarded the firmament of the fixed stars, the ​boundary of the universe, as motionless. He believed the planets to be enclosed in a series of concentric permanent spheres. But notwithstanding this he prepared the way for a radical change in the theory of the universe. Facts which apparently rested on the direct evidence of sense perception and were supported by the most famous authorities must now be regarded as discredited! We must awaken to the fact that the system of things which constitutes the universe admits of a different interpretation from the apparent demands of sense perception.
4. Giordano Bruno (1548-1600) is at once the most profound and the most courageous thinker of the renaissance period. Strongly influenced by the philosophy of antiquity and accepting the theories discovered by Cusanus and Telesius, he found a real foundation for his theory of the universe in the new astronomy, as elaborated by Copernicus and later by Tycho Brahe.
Born at Nola in southern Italy, Bruno entered the Dominican order in his early youth. He was soon charged with heresy. His active mind and restive spirit could not endure the rigid monastic discipline. He fled the cloister, discarded the monastic garb and began a wandering career of study and travel, which took him to Switzerland, France, England and Germany. He appears in the capacity of teacher in Toulouse, Paris, Oxford and Wittenburg; but nowhere did he find a permanent position. This was due in part to the opposition of the traditional schools, and in part to his restless disposition. But despite his wanderings he found time to write his ingenious works, among which the Italian dialogues, published in London 1584, deserve special mention. He never regarded reconciliation with the Catholic church ​as impossible, and even cherished the hope of returning to Italy and, without re-entering the cloister, continuing his literary activities. He felt that his career north of the Alps was a failure and Protestantism, with its many little popes, was more reprehensible to him than the ancient church with its single Pope. He finally returned therefore, but was arrested by the Inquisition at Venice (1592) and, after a long imprisonment, burnt as a heretic at Rome in 1600. He died like a hero.
Bruno held Copernicus in high esteem because of his lofty mind. It was he who had lifted him above the illusory testimony of the senses to which the vast majority remained enchained. But notwithstanding his unstinted admiration for the man, he nevertheless regarded the Copernican theory as inadequate because of its conception of the universe as bounded by the sphere of the fixed stars. The basis of Bruno’s opposition to this theory was two-fold, its failure to accord with his theory of knowledge together with his religio-philosophical views.
a. The sensory evidence of an absolute world-center and an absolute world-boundary is merely apparent. The moment we change our viewpoint we attain a new center and a new boundary. Every point in the universe can therefore be regarded at once as both central and peripheral. Abstract thought and sentiency agree in this; namely, that we may add number to number, idea to idea, ad infinitum, without ever approaching an absolute boundary. The possibilities of progress in knowledge are therefore unlimited, and it is from this characteristic of knowledge (la conditione del modo nostro de intendere) that Bruno conceives the character of the universe: absolute boundaries are as inconceivable of the universe as of knowledge. ​It follows therefore that there are no absolute positions. Every position is determined by its relation to other positions. One and the same point may be either center, pole, zenith or nadir—depending entirely on the point from which it is observed (respectu diversorum). There can therefore be no absolute motion and no absolute time. The ancients based their theory of absolute time on the absolute regularity of the motions of the fixed stars; but since the motions observed from any particular star differ from that of another star there are as many times as there are stars. And, finally, the traditional theory of absolute heaviness and lightness is likewise an error; its tenability was based on the presupposition of an absolute center of the universe. Heaviness and lightness must therefore be understood with reference to the various world-bodies. Sun particles are heavy in relation to the sun, earth particles in relation to the earth. According to Bruno, heaviness is the expression of a natural impulse within the parts to return to the greater whole to which they belong.
The principle of relativity is closely connected with the theory that nature is everywhere essentially the same. We can infer the conditions in other parts of the universe from the conditions about us here on the earth. We observe e.g. that ships, when seen at a distance, appear to be motionless, whilst as a matter of fact they are moving very rapidly, and thus by analogy we may assume that the fixed stars appear to be motionless by reason of their great distance from us. There is no justification for maintaining the fixity of the firmament dogmatically as the ancients and even Copernicus had done.
Bruno therefore challenged the dogmatic principles which Copernicus had still accepted. He saw very clearly ​however that the matter cannot be definitely determined by mere speculative generalizations; genuine proof can only come from the discovery of new facts of experience. And he believes furthermore, and rightly so, that no one can investigate the matter without prejudice who adheres dogmatically to the traditional hypothesis.—At one important point he was able to appeal to well-defined facts. He rejected the theory, still accepted by Copernicus, that the stars are enclosed in permanent spheres: If the earth can move freely in space, why should it be impossible for the stars to do the same? And he found his conclusion verified by Tycho Brahe’s investigation of comets, which as a matter of fact pass diagonally through the “Spheres” whose crystal masses were supposed to separate the various parts of the universe! It follows therefore that the contrast of heaven and earth, of permanent and changeable parts of the universe, is untenable.
b. In his philosophy of religion Bruno starts with the infinitude of the Deity. But if the cause or principle of the universe is infinite it must follow that the universe itself is likewise infinite! We are unable to believe that the divine fullness could find expression in a finite universe; nothing short of an infinite number of creatures and worlds would be an adequate display of such fullness.
Bruno elaborated his theory of the infinity of the universe in two dialogues, the Cena de la ceneri and Del’ infinito universo e mondi (1584), and in the Latin didactic poem De immenso (1591). These works are of epochal importance in the history of the human mind. Just as this wide expanse inspired in Bruno a feeling akin to deliverance from the confines of a narrow cell, so the human mind is now presented with a boundless ​prospect forever promising new experiences and new problems.
c. Bruno elaborated his general philosophical principles, which were naturally closely related to the new world theory, in the dialogue De la causa, principio e uno (1584).
Inasmuch as the new world theory annulled the opposition between heaven and earth, Bruno undertakes the task of annulling all oppositions by means of a profounder speculation. Sharp antitheses originate in the human mind and there is no ground for ascribing them to nature. Plato and Aristotle e.g. had no warrant in objective fact for assuming a distinction between Form and Matter. There is no absolute Matter, just as there is no absolute position and no absolute time. Absolute Matter must necessarily be absolutely passive, in which case it could acquire form and development only through some external agency. But in the natural world Forms are not introduced into Matter from without, after the manner of a human artist; they originate from within by an evolution of nature’s own inherent energy. Matter is no less divine than Form and it persists in constant change even as the ancient Atomists had observed. Nature reveals a constant cycle from inorganic matter through the organic processes and back again to the inorganic. According to Bruno’s own statement, he was so profoundly impressed with this idea for a while that he was inclined to regard Forms and the spiritual factor in the universe as unessential and ephemeral. Later on however he perceived that Form and Spirit, no less than Matter, must have their ground in the infinite Principle. He admitted that everything must contain a spiritual principle, at least potentially (secondo la sostanza), even ​if not always actually (secondo l’atto). The ultimate source of all things consists of a Being which transcends the antitheses of Matter and Form, potentiality and reality, body and mind. In so far as this ultimate source is conceived as something distinct from the universe it is called “Cause,” in so far as it is conceived as actively present in natural phenomena it is called “Principle.” The Deity is not a far distant being; it reveals its presence in the impulse towards self-preservation and it is more intimately related to us than we are to ourselves. It is the soul of our soul, just as it is the soul of nature in general, which accounts for the all-pervasive interaction throughout universal space.
The culmination of thought likewise marks its limit, because we are incapable of thinking without antitheses. Every conceptual definition imposes certain limitations; the infinite Principle is therefore incapable of definition. Theology must forever remain a negative science, i.e. a science which eliminates the limitations and antitheses from the concept of Deity. The only significance which positive theology can have, i.e. a theology which undertakes to express the infinite Principle by definite predicates, is practical, didactic and pedagogic. It must address itself to those who are incapable of rising to a theoretical contemplation of the universe. God is indeed more highly honored by silence than by speech.
d. The ideas described above are characteristic of the most important period of Bruno’s philosophical development. It is possible however (with Felice Tocco, in his valuable treatise Opera latine de G. Bruno, 1889) to distinguish an earlier and a later period in his development. During the first period Bruno’s philosophy had somewhat of a Platonic character, in that he regarded general ideas ​as the highest object of knowledge and the universe as an emanation from Deity (De umbris idearum, 1582). But his ideas apparently mean something different from the universal concepts (as in Plato). He seems rather to regard them as laws which describe an actual relationship (e.g. between the different parts of the body).—The last period, as is evident from the De triplici minimo (1591), is noteworthy for its emphasis on the individual elements of being between which this actual relationship obtains. Sensory objects consist of parts notwithstanding the apparent continuity perceived through sense perception. Bruno calls the ultimate, irreducible (or first) parts atoms, minima or monads. There are various classes of monads, and he even calls the universe and God monads, when speaking of them as units.
The distinctions between Bruno’s three points of view—the theory of Ideas, the theory of Substance, and the theory of Monads—however are simply matters of degree.
e. Bruno’s ethics conforms with his general theory of the universe. His Spaccio de la bestia trionfanta (1584) evaluates human virtues according to a new standard. Its dominant characteristic is the prominence given to the desire for truth and to honest toil. Every correct evaluation presupposes truth, and toil is the natural consequence of the task imposed upon man, not merely to follow nature, but to bring forth a new, higher order of nature, that he may become lord of the earth. In the Degli eroici furori (1585) Bruno describes the heroic man as one who is aware that the highest good can only be realized through strife and suffering, but who never despairs, because pain and danger are evils only from the viewpoint of the world of sense, not from the viewpoint of eternity (ne l’occhio del eternitade). The possibilities ​of pain increase with the height of the aim. But the heroic man finds his joy in the fact that a noble fire has been kindled in his breast—even though the goal should be impossible of realization and his soul should be consumed by its profound yearning. This courageous wisdom typifies Bruno’s character as it appears in his life and in his heroic death at the stake.

##### C. The New ScienceC. The New Science

Without any disparagement of the tremendous importance of the free investigations in the sphere of mental science, or even the radical change in the general theory of the universe, the fact nevertheless remains that the founding of modern natural science had a far profounder influence upon human life. The contributions of antiquity are likewise in evidence here, particularly the study of the writings of Archimedes. The real cause however must be traced to the increasing interest in the industries, mechanics and engineering operations, especially in the Italian cities. Galileo makes mention of this fact at the opening of his chief work. It was but natural therefore that this should give rise to a desire to understand the laws and principles by which to promote these operations. Then followed a transition from the achievements of man to the majestic products of nature, because man depends, more or less consciously, on the analogy between human mechanics and the efficiency of nature.
Modern natural science created a new method. It substituted observation and experiment together with analysis and computation for speculation and dogmatic construction on the one hand and the mere collection of facts on the other. The human mind evolved new functions, whose nature and value necessarily suggested new ​problems in the philosophy of knowledge. Owing to the fact that the new method was applied almost exclusively to the realm of matter, the concept of matter naturally came to the foreground. And as a matter of fact it was not until then that the problem of the relation of mind and matter could be sharply and definitely stated. Ethics and the philosophy of religion likewise received their complement of new data. The self-sufficiency of man was magnified. New forms of social life were evolved, especially through the progressive division of labor made possible and necessary through the mechanical inventions. The growing conviction of the prevalence of fixed natural laws required a restatement and a more precise definition of the problem of religion. Man’s general attitude to the universe, both in its theoretical and its practical aspects, underwent a most remarkable change.
We shall mention three men as the real founders of modern science.
1. Leonardo da Vinci (1452-1519), the famous artist, whose varied talents made him one of the most remarkable characters of the Renaissance period, is known to us through several fragments in natural science and philosophy which are of great importance. His manuscripts became scattered and none were published until late in the nineteenth century. (H. P. Richter has published a good collection. London, 1883. A German translation of the most important fragments was published by M. Herzfeld, Leipzig, 1904.)
Experience is the common mother of all knowledge. But we cannot stop on the plane of mere observation. We must find the internal bond of nature (freno e regula interna) which explains the vital relation of things and events. And the only possible method of doing this is ​by the aid of mathematics. Mathematical deduction is the only method of discovering the unknown from the given facts of nature. We thus find even here a clear expression of all the characteristics of modern method, viz. the proper coordination of induction and deduction.—Certain statements of Leonardo’s indicate a sturdy naturalism. The only thing we can know about the soul is the nature of its functions and its activity as an organic principle; whoever cares to know more must inquire of the Monks! Nature consists of a majestic cycle between the inorganic and the organic, and between the animate and the inanimate. Nature always takes the simplest course. There is reason therefore to hope for a great future with respect to the knowledge of nature.—Leonardo suggested a number of interesting anticipations of the principle of inertia and of energy. He stands solitary and alone in his own age. It was not until a century later that any advancements were made along the lines which he indicated.
b. John Kepler (1571-1630), the famous astronomer, is an interesting example of the evolution of an exact scientific conception of nature from a mystic-contemplative starting-point. His first treatise (Mysterium cosmographicum, 1597) is based on theological and Pythagorean principles. The universe is the manifestation of God. The paths and motions of the heavenly bodies must therefore reveal certain harmonious and simple geometrical relations. The Holy Ghost is revealed in the harmonious ratio of magnitudes of stellar phenomena, and Kepler thinks it possible to construe this magnitudinal ratio. Later on however he simply maintained the general belief that certain quantitative ratios must exist between the motions of the planets and formulated the results deduced from ​Tycho Brahe’s observations in the laws which bear his name. He afterwards demonstrated the quantitative ratios on the basis of the facts of experience. Here his method involved the combination of the experimental with the mathematical method. Just as he had at first established the principle that nature conforms to mathematical laws by the theological method, so he further believes that the planets are guided in their course by separate planetary souls, even as the entire world-system is directed by the world-soul which dwells in the sun. His explanation of nature therefore was thoroughly animistic or mythological. Later on in life he held that science must make no assumptions except such as can be actually deduced from experience. He calls such causes vera causa. He also rejected the idea of planetary souls which as a matter of fact are never actually given in experience. In his Astronomia nova s. physica coelestis (1609) he makes the transition from theology and animism to pure natural science. He defends his belief in the importance and truth of the quantitative method psychologically and empirically as well as theologically. Mathematical knowledge is the clearest and the most certain knowledge which we possess and it becomes us therefore to apply it as widely as possible. The processes of nature are qualitatively modified by our subjective states (pro habitudine subjecti). Perfect certainty and objectivity can only be attained by the quantitative method. And, finally, experience reveals the fact that all material phenomena have quantitative, especially geometrical, attributes; “the method of measurement can be applied wherever there is matter” (ubi materia, ibi geometria). As a matter of fact the universe participates in quantity (mundus participat quantitate).
Kepler elaborates his general conception of scientific ​method in his Apologia Tychonis. All science is based on hypotheses. But hypotheses are by no means to be regarded as arbitrary notions. They must vindicate their title by the harmony of their logical consequences with the given facts and the consistency of their implications. Science begins with the observation of facts, uses these data for the formulation of hypotheses and finally seeks to discover the causes which account for the uniformity of events.
c. Galileo Galilei (1564-1642) is the real founder of modern science, because he shows the clearest understanding of modern methods—the method of induction and deduction as mutually complementary.
If induction demanded the examination of every possible case, inductive inference would be impossible. But it is possible to examine a number of characteristic cases, and formulate a hypothetical principle by an analysis of these cases, and finally prove that the consequences deduced from this principle are in accord with experience. In order to make this deduction and show its agreement with the facts correctly we must be in position to state our facts in quantitative terms. We are therefore under necessity of measuring phenomena exactly. Galileo raised the watchword; Measure everything which is measurable and reduce the things which will not admit of direct measurement to indirect measurement.
Kepler had previously shown that matter cannot of itself pass from rest to motion. Galileo advances a step farther. According to the principle of simplicity,—which, like Copernicus, Bruno and Kepler, he regarded as a universal law—he maintained that a body tends to remain in its given state so long as it is unaffected by external influences. A body can therefore of itself neither change its ​motion nor pass from motion to rest. In the absence of all external influences a moving body would continue its motion indefinitely at the speed originally given. This as a matter of course represents an ideal case, since absolutely empty space is unrealizable, but Galileo showed by the experiment of rolling a ball in a parchment groove that the length of time the ball continued in its course was in direct proportion to its own smoothness and the smoothness of the parchment. In this way he proved the principle of inertia. But Galileo likewise thought that circular motion, which he also regarded as simple and natural, as well as motion in a straight line, would be continuous if all external obstacles could be eliminated. In his investigations of the motion of falling bodies he likewise starts with the principle of simplicity, with a view to showing later that it is verified by observation and experiment. “If a stone, falling from a given position at considerable height, accelerates its speed, why should I not regard the acceleration as due to its simplest explanation? And there is no simpler explanation of acceleration than that of a continuously uniform increase.”—It follows further from the principle of inertia and the law of falling bodies that we must take account of the energy or the impetus of motion (energia, momento, impetu) present at each moment as well as the actual sensible motion.
Galileo elaborated the modern theory of motion, which forms the basis of physics, in his Discorsi della nouve scienze (1638).—His Dialogo sopra i due massimi sistemi del mondo (1632) draws a comparison between the Ptolemaic and Copernican world-systems, without, as he thought, taking sides, but in such a way as to leave no doubt as to his real opinion. This brought on the catastrophe of his life. He had even previously (after the discovery of the moons of ​Jupiter and of sun-spots) expressed himself publicly as favoring the Copernican system. When the College of the Inquisition, therefore, in the year 1616, placed Copernicus’ book on the Index, he is said to have promised Cardinal Bellarmin that he would neither defend nor disseminate the Copernican theory. He denied that the Dialogo was a violation of this promise on the ground that he had expressed himself hypothetically. But the book was forbidden, and the old man of seventy was required—under threat of torture—to solemnly abjure “the false doctrine,” that the earth is not the center of the universe and that it moves. The Inquisition held him under suspicion for the rest of his life and he was forced to have his works published in foreign countries.
It has already been observed that the Copernican theory beautifully illustrates the unwisdom of accepting our ideas as the expression of reality without further question. Galileo emphasized this phase of the new theory very strongly; “Think of the earth as having vanished, and there will be neither sun-rise nor sun-set, no horizon even and no meridian, no day and no night!” Later on he expanded this idea so as to include the whole of physical nature. In the Dialogue he takes occasion to observe that he had never been able to understand the possibility of the transubstantiation of substances. When a body really acquires attributes which were previously lacking, it must be explained by such a rearrangement of its parts as would neither destroy nor originate anything. This clearly asserts the principle that qualitative changes can only be understood when referred to quantitative changes. Galileo had already stated this view even more strongly in one of his earlier works (Il saggiatore, 1632). Form, magnitude, motion and rest constitute all that can be said of ​things; they are the primary and real attributes of things (primi e reali accidenti). Our disposition to regard taste, smell, color, heat, etc., as the absolute attributes of things, on the other hand, is due to sense-prejudice. We give these names to things when they furnish the occasion of certain sensations, but these sensations take place within our bodies. They do not inhere in things. They would vanish if the corpo sensitivo were to vanish.—This doctrine, which contains the principle of the mechanical conception of nature, acquired vast importance in the investigations into the theory of knowledge in the following period.