# A Brief History of Modern Philosophy/Book 3

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### THIRD BOOK english empirical philosophyTHIRD BOOK english empirical philosophy

The great system builders did indeed begin with analysis, but the foundations upon which they built were concepts and presuppositions just the same, and these were not carefully investigated. This is specially true of the principle of causation and several of the principles of natural science, which were regarded as self-evident. The method of using presuppositions without inquiring into their validity has, since the time of Kant, been called dogmatism. It is the great merit of English philosophy that it instituted an investigation of the presuppositions of knowledge. It investigates the psychological processes which give rise to these presuppositions, as well as the methods of demonstrating their validity. The problem of psychology and the theory of knowledge thus come into the foreground, and the problem of being gradually recedes into the background.
The consequences of this transposition of problems were of great importance in other departments as well as in the spedtic domain of philosophy. People began to demand a definite account, not only of scientific presuppositions, but also of the principles which were regarded as fundamental in politics, religion and education. Authorities, which had hitherto been accepted without hesitation, must now give an account of their origin and their trustworthiness. Stated in philosophical terms this means that the problem of evaluation now became more prominent than formerly. This is a matter that can neither be solved by an appeal to authority nor by a mere ​deduction from theoretical principles, but requires a method of treatment peculiarly its own. The foundation of ethics likewise receives independent treatment more frequently than hitherto.
1. John Locke (1632-1704) devotes his chief work, the Essay Concerning the Human Understanding (1690) to the investigation of the nature and validity of human knowledge. The first draft of this pioneer work was brought about by a discussion of moral and religious subjects. When it became evident how difficult it is to arrive at definite conclusions, the thought occurred to Locke that they must first of all examine the faculty of knowledge, in order to see what subjects it is capable of treating, and moreover what things are beyond its powers. In the first book Locke criticizes the doctrine of innate ideas, especially in the form in which it was held by Herbert of Cherbury; in the second book he shows that all ideas come from experience, and reduces compound ideas to their simple elements; in the third book he investigates the influence of language on thought; and in the fourth he examines the different kinds of knowledge and defines its limits.
John Locke received a splendid education from his father. He pays a beautiful tribute to his father in his splendid essay On Education (1692). But the formal grammatical discipline and the scholastic instruction received at school and the university were repulsive to him.. His philosophical development was influenced chiefly by the study of Descartes, Gassendi and Hobbes. Being unable to subscribe to the 39 Articles, he had to relinquish his original plan of becoming a clergyman. He afterwards studied medicine, but soon entered the service of the Earl of Shaftsbury, with whose family he remained ​connected for two generations, as tutor, secretary and friend. At the fall of the Earl, Locke went to Holland, where he composed his most important works and likewise participated in the preparations for the revolution. He returned to England with William of Orange, and helped to formulate the policies of the new administration. He spent his last years in rural solitude.
a. In Locke’s terminology idea represents everything with which we are occupied when engaged in thought. Some have supposed that certain ideas, especially the idea of God and the logical and moral principles, are innate, but experience shows that children, primitive races and the illiterate possess nothing more than particular and sensible ideas. There are men who have no idea of God and no real ideas of morality. Some of our ideas are natural, i.e. such as have been acquired through experience by means of our native faculty; but even these are not innate. Locke attributes the doctrine of innate ideas to human indolence, which shrinks from the labor involved in exploring the origin of ideas.
All ideas, all the elements of consciousness originate from two sources: external experience (sensation) and internal experience (reflection). In external experience a physical impression produces a sensation (perception) in the soul; in internal experience we observe the activity of our own mind in elaborating the sensations received from without.
In the acquisition of simple ideas consciousness is for the most part passive. Simple external ideas are of two kinds: ideas of primary and of secondary qualities. The primary qualities can be attributed to the external objects themselves; such are solidity, extension, figure, mobility. Secondary qualities belong only to our ideas, ​they are not attributes of the things themselves; they are the results of the influences of primary qualities on us. Such secondary ideas are light, sound, smell, taste, &c.— We have previously met with this distinction in Galileo, Descartes and Hobbes. Locke adopted it from Boyle, the noted chemist, who is the author of the terms "primary and secondary qualities."
Whilst we are largely passive in acquiring simple ideas, we are active in forming from them, first, complex ideas, second, ideas of relations, third and finally, abstract ideas. Hence there are three forms of activity: composition, association and abstraction. We combine simple ideas into a single idea whenever we form ideas of attributes (modes), such as space and time, energy and motion. The ideas of such attributes as sensation, memory and attention are formed in inner experience. We form our ideas of things or substances by combining ideas of modes. But here a mystery confronts us. We know the single modes by themselves, but we are unable to tell what substance, which presumably supports the modes, really is. We may likewise place two ideas in juxtaposition, without forming a compound idea. We do this in all cases of ideas of relation, such as cause and effect, time and space relations, identity and difference.— Finally we are active also when we abstract or isolate an idea from its original connection. This happens when we form an idea of a color in general, or the idea of space without reference to its content.
b. Touching the matter of validity, Locke holds that there can be no question in the case of simple ideas because they are the direct effect of external objects. Even secondary qualities, which do not represent objects, are nevertheless the direct results of objective impressions. ​The matter stands quite differently however when we come to consider the validity of the ideas which we ourselves produce (in the three ways noted above) ! They cannot of course be copies or impressions! We use them however as archetypes, or patterns, with which to make comparisons. In this case, therefore, we estimate objects from the viewpoint of their agreement or disagreement with the patterns of our own construction. But compound, relative and abstract ideas furnish no information whatever as to the real nature of things. It is in this sense that we use figures in mathematics, and moral ideals in ethics. The proofs of mathematics and moral philosophy are wholly independent of the existence of the things to which they refer. But such is not the case with the idea of substance, which is expressly intended to indicate an external object. The validity of ideas of this kind can only be established therefore on the basis of a complex of attributes given in experience, or if, as in the case of the idea of God, we are in position to offer a separate proof for its validity.
In agreement with Descartes, Locke distinguishes between intuition and demonstration. Intuition merely furnishes us knowledge of self and of the simplest relations between our ideas. The combination of a series of intuitions results in demonstration. These two kinds of knowledge alone are fully certain; sense experience is always only probable. Locke proves the existence of God by appealing to the principle of causality: The world must have a cause, and, since matter cannot produce spirit, the cause of the universe must be a spiritual being. He regards our knowledge of the causal principle itself as an intuition, i. e. as self-evident. At this point he agrees with the dogmatic systematizers. Hence he ​likewise employs this principle complaisantly both in his proof of the validity of simple ideas and of the existence of God. But the causal idea on the other hand belongs to the class of relative ideas, which is therefore a subjective construction albeit on the basis of sense-perception. Locke is rather ambiguous at this point (as also on the idea of substance). The profound problems involved in these ideas were not discovered until Locke's successors (Berkeley and Hume) came upon them.
c. In the philosophy of law, Locke (in the Essay on Government (1689) makes a sharp distinction between political and patriarchal authority. Political authority consists in the authority to prescribe laws, to enforce the laws which are prescribed, and to protect society against foreign enemies. Such authority can be established only by unconstrained agreement, which may however be tacitly concluded. It is the duty of the state to secure liberty, which, in a state of nature, is constantly in danger of being lost. If the government proves unfaithful to its trust, the people have the right to overthrow it.
In his philosophy of religion (The Reasonableness of Christianity as Delivered in the Scriptures, 1695) Locke conceives revealed religion as a more developed form of natural religion. Whether or not anything is revelation must be decided by reason. Revelation is necessary, however, on account of the fact that man has not used his reason properly and has consequently fallen into superstition. An elaborate system of doctrine is unnecessary. The illiterate and the poor, whose lives are spent in bitter toil, readily understand the example and teachings of Christ. The English Free-thinkers (the so-called Deists) developed Locke's philosophy of religion more fully in the direction of a more pronounced rationalism. ​The most important representative of this tendency was John Toland (1670-1720), who says, in his Christianity Not Mysterious (1696), that there is nothing in the Gospel which either transcends or conflicts with reason; but that priests and philosophers had transformed Christianity into a mystery. In his Pantheisticon (1720) he describes pantheism as the private theory of a society of enlightened gentlemen, who conceive God as the efficient energy of the universe. His most important book is the Letters to Serena (1704), in which he says, against the Cartesian and Spinozistic conception of nature, that motion is an attribute of matter which is equally primary with extension. Motion persists everywhere in nature, and all rest is only apparent.
2. Neither Locke nor the great systematizers of the seventeenth century had fully accepted the sublime ideal of knowledge proposed by Kepler and Galileo. They still regarded experience and reason as mutually exclusive. It was all the more significant therefore that Sir Isaac Newton (1642-1727), in his Principia Philosophiæ Naturalis Mathematica (1684), should furnish the most famous product of exact empirical science by means of a combination of induction and deduction. This work had a decisive influence on the further development of philosophy. But this is not the only ground for making reference to Newton in the history of philosophy. He is likewise the author of certain characteristic philosophic ideas.
Starting from the fact that weight is greater in the valley than on the mountain tops, and that all bodies which are tossed upward drop to the earth, Newton formulated the hypothesis that the heavenly bodies are also heavy and that they deviate from the direction implied by the ​law of inertia according to a ratio which corresponds to the law of falling bodies at the earth's surface. He then deduces the mathematical consequences of this idea and finally shows that the results of this deduction agree with the facts as actually observed. From this he concludes that the motion of the heavenly bodies is governed by the same law as falling bodies. He calls the energy which manifests itself in this law attraction (attractio). He does not introduce any mystical energy. By attraction he means only an energy which acts according to the well-known law of falling bodies—which likewise constitutes the energy.—As a matter of fact he was later inclined, and his disciples even more so, to regard attraction as an original energy proceeding directly from God.
The expositions of Newton’s masterpiece likewise involve presuppositions and speculative ideas which are of philosophical importance. He makes a distinction between "absolute, true, and mathematical space" and sensible spaces. Absolute motion occurs in the former alone, because it contains absolute places (loca primaria), places which are at once places for themselves (sine relatione ad externum quodvis) as well as for other things. Following Copernicus and Kepler , Newton defends the ancient theory of absolute space. He does not simply regard the mathematical method of interpretation as a way of looking at things, which may be regarded as mathematically fundamental, but rather as the true method of interpretation in contrast with the popular or common-sense method. And he even connects this with religious ideas: Space is the sensorium dei, the instrument of the divine omnipresence.
Newton proves the existence of God from the purposeful and harmonious arrangement of the universe, which is ​peculiarly revealed in the simple and uniform arrangement of the solar system. He asserts most emphatically that the wonderful structure (elegantissima compages) of the solar system—the orbital motions of the planets around the sun, which are concentric with the orbit of the sun and lie almost in the same plane— is inexplicable on the basis of natural law. The orbital motion can only be explained by reference to supernatural energies. Left to themselves, the planets would fall into the sun!— The remarkable structure, the organs and the instincts of animals furnish additional evidence of the supernatural! (Besides the Scholiimi generale contained in the Principia Newton expressed himself on these matters in his Optics, Queries 28-29, and in his letters to Bentley.)—But Newton did not think that the mechanism of the universe was finished once for all. God must interpose as an active regulator from time to time. This problem was the occasion of a very interesting discussion between Leibnitz and Clarke, one of Newton’s disciples.
3. George Berkeley (1685-1753) occupies a place in empirical philosophy similar to that of Leibnitz in the group of systematizers. He represents a reaction against Locke and Newton similar to that of Leibnitz against Descartes, Hobbes and Spinoza, and, like Leibnitz, Berkeley not only represents a reaction, but an advance and further development. He aimed to refute the conclusions of the new science which were hostile to religion, and he hoped to accomplish this by a criticism of the abstract concepts and by a return to immediate experience and intuition. Childlike piety and acute critical analysis have rarely been so intimately united as in this clear mind. At the University of Dublin he occupied himself with the study of Locke, Boyle and Newton, and his chief works were ​composed while he was yet but a young man. He afterwards entered the Anglican church and participated in the controversy against the Free-thinkers. His missionary zeal inspired an interest in America, and he conceived a plan of founding a college in America. The sublime ambition to which he devoted the best years of his life comprehended not only the conversion of the Indians, but likewise the regeneration of science and art in the western hemisphere. He was forced to give up his plan however after a three years' sojourn in America. He afterwards served as Bishop of Cloyne in Ireland, equally zealous as pastor, philanthropist and patriot.
In his chief work. The Principles of Human Knowledge (1710), Berkeley shows that, strictly speaking, we cannot form any general ideas. His criticism is directed particularly against Locke ’s theory of "abstract " ideas. We can form an idea of part of an object without its remaining parts, but we are unable to form new separate ideas which are supposed to contain that which is common to several qualities, e. g. an idea of color in general, which should contain that which is common to red, green, yellow, &c. If I wish to have an idea which may be applied to a whole series of things which are qualitatively different, I must either use a sign, e. g. a word, or, what amounts to the same thing, regard a simple member of the series as representative or typical.
The idea of matter conceived as a general idea is fallacious. Matter is supposed to be the basis of sensible attributes. Suppose we grant that secondary attributes have only subjective significance: it must follow that matter can only be described by means of its primary attributes. But how can we have an idea whose content ​is nothing more than extension, mobility, divisibility and solidity? The objects which are really given in experience, and which we are able to perceive, always appear under secondary attributes, they can be seen, heard, touched, &c. The primary attributes are never given independent of the secondary attributes. And moreover an investigation of our conception of space, which Berkeley made in his Theory of Vision (1709), reveals the fact that we form our ideas of space in part by means of the sense of vision, and in part by means of the sense of touch (with which Berkeley also includes the so-called sense of motion). Our idea of space, particularly of distance and magnitude, is formed by a fixed combination of ideas of vision and touch, because the visual image invariably suggests a certain idea of touch. We discover that we can also touch the things which we see, on the single condition that we perform the necessary movements. Hence we suppose that we sense distance and size immediately. Space as such cannot be perceived any more than color as such. Which of the two spaces which we actually know— visual or touch space— shall we regard as "absolute" space? We are unable to form an idea of anything which is common to these two spaces. And matter, being chiefly characterized by the attribute of extension, must therefore share the same fate as space.
By this radical method Berkeley annihilates materialism. But he denies most emphatically that this abolishes the distinction between illusion and reality or destroys the possibility of natural science. Our knowledge of reality depends on distinguishing sensation from imagination, and the criteria for this distinction are very definite; sensations are generally more intense and more distinct than images. They take place in an invariable and ​uniform order, whilst images, are fitful and irregular; and we are conscious of not having produced the sensations ourselves. The problem of natural science therefore consists in discovering the exact uniform relation which obtains between our sensations, so that the presence of a sensation shall indicate to us what other sensation we may expect. The interpretation of nature therefore simply means the discovery of the laws which govern the relations of our sensations. With matter in general, that indefinite something which is supposed to underlie all sensations, science has nothing whatever to do.
Berkeley nevertheless thinks that sensations necessarily require a cause which is distinct from ourselves. In attempting to formulate an idea of this cause, he starts from an analogy with our own activity. Our own faculty of producing and changing ideas is the only activity of which we have knowledge. Berkeley calls this faculty the will and regards the will as the essence of the soul: the soul is the will (Commonplace Book). He also conceives the causes of our sensations after the analogy of this will: these are produced immediately by God. Thus Berkeley’s philosophy passes over into theology. This immediate relationship with God satisfies his religious feelings. He regards the idea that God should first have created matter and then ordained that it should influence our minds as unnecessarily circuitous.— The divine will is not only evident in the separate sensations, but likewise in their uniform sequence, and the teleology of phenomena reveals the divine prescience.
Berkeley elaborates his philosophical ideas in popular form and in polemical controversy against the Free-thinkers in two beautiful and ingenious dialogues (Dialogues between Hylas and Philonous, 1712, and Alciphron, 1732). ​4. Anthony Ashley Shaftesbury (1671-1713) introduced a new tendency in the moral philosophy of the modern period. During the period of reaction against the Middle Ages the custom of basing ethics on individualism—the emphasis of the rights of the individual—was almost universal. Magnanimity and sublimity of thought were regarded as the highest attributes of character. Such was the case with Telesius, Bruno, Descartes, Hobbes and Spinoza. Shaftesbury, on the contrary, emphasized spontaneous emotion, the instinctive impulse to complete devotion. He was a grandson of the famous statesman of the same name, the patron of Locke, and Locke had been his tutor. But he had also been introduced to the classical languages and literature at an early age, and he was profoundly affected by the ancient ideas of harmony, especially as developed in later stoicism. Both from taste and on account of feeble health he lived quietly, devoting himself to his literary pursuits, or to travel.
According to Shaftesbury there is no absolute opposition between nature and culture or between self-assertion and devotion or loyalty. An involuntary impulse unites the individual with the whole race, just as naturally as the instincts lead to the propagation of the species and care for the young. But thought, deliberate reflection, however is not superfluous on this account. It is through reflection that we become conscious of a spontaneous impulse and as a matter of fact this is the only way in which affections, such as the admiration of nobility of character and contempt for the ignoble, can possibly arise affections which bear a close relation to the appreciation of beauty except that they bear more of an active character. But such an affection (reflex affection, moral sense) is nevertheless natural because it is evolved ​from natural instincts. The conditions of human life are such that we are working for our own interests whenever we are concerned for the common welfare, and the happiness which we procure for others returns upon ourselves. The problem that remains is the further development of this harmony between self-assertion and devotion. Whatever is conducive to social harmony likewise produces harmony in the soul of the individual and this subjective beauty has an inherent value which renders egoistic awards and theological sanctions superfluous. A splendid harmony likewise pervades the universe in general, but due to our limited vision we sometimes fail to discern it. Shaftesbury collected his most important writings under the title Characteristics of Men, Manners, Opinions and Times (1711). Rand has recently (1900) published one of Shaftesbury ’s essays. Philosophical Regimen, which was hitherto unknown. The background of his ethical ideas, formed by his faith in the harmony of the universe, receives even greater emphasis in this than in his other writings.
The ideas advanced by Shaftesbury received a more systematic treatment at the hands of Francis Hutcheson (1694-1747). Hutcheson was professor of moral philosophy at the University of Glasgow and his ideas were thus introduced into the Scottish Universities. He too places the chief emphasis upon immediate feeling. Reason is a faculty whose function it is to discover the means for the realization of our purposes. Indispensable though it is to the moral feelings, if these are not to act blindly, it is nevertheless not the final court of appeal in matters pertaining to morality. Experience is likewise a necessary condition for the successful operation of moral feeling; this can only take place on the basis ​of clear observations. Nevertheless moral feeling does not therefore proceed entirely from experience. But under the guidance of reason and experience it ascribes the highest value to such actions as produce the highest degree of happiness to the greatest number of men. (The importance of the personages may however supplant the number.) Thus Hutcheson was the first to propound (in his Inquiry into the Ideas of Beauty and Virtue, 1725) the famous principle of "the greatest happiness for the greatest number." Like Shaftesbury, Hutcheson was strongly influenced by the ethics of the Greeks, especially as it appears in the later Stoics. This whole trend in modern ethics is, on the whole, an interesting form of the renaissance movement. W. R. Scott’s recent monograph on Hutcheson contains a suggestive treatment of the whole movement.
According to Hutcheson, moral feeling is divinely implanted. But its operation is not limited to those who believe in God. Ethics therefore is wholly independent of theology.—The sense of duty arises when moral feeling is momentarily in abeyance but we are at the same time conscious that a proposed act would bring us into conflict with human love and thus rob us of inner peace (serenity) of mind.—Hutcheson's System of Moral Philosophy contains a comprehensive elaboration of his ethical theories.
Bishop Joseph Butler (1692–1752), in deliberate opposition to the optimism and theory of harmony advocated by Shaftesbury and Hutcheson, emphasizes the distinction between moral feeling, which he prefers to call conscience, and the other human elements and impulses. Conscience, as a matter of course, acts directly and is combined with a sense of inner satisfaction, as in the case of obedience ​to a profound impulse. We require a religious sanction (Sermons, 1726), however, in order to resist doubt and the questions which arise in our calmer moods. Whilst Shaftesbury bases his optimism on Being or Nature as a whole and assails Christianity on account of its inconceivability and its inhumanity, Butler maintains that the view of nature in which so many rudimentary ambitions must perish and the innocent so frequently suffer instead of the guilty violates the belief in a universal harmony, and that the criticisms charged against Christianity must likewise apply to the natural religion which Shaftesbury professes. (Analogy of Religion, natural and revealed, to the constitution and course of nature, 1737.)
The Frenchman, Bernard de Mandeville (c. 1670-1733), who was born in Holland and lived in London as a practicing physician, likewise opposed Shaftesbury's optimism. In The Fable of the Bees (1705) and in the notes which he afterwards appended to this story he says that private virtues are of no benefit whatever, either from the viewpoint of culture or the general welfare of society. On the contrary, the desire for pleasure, impatience and egoism are motives which inspire effort, culture and social organization. It is the duty of statesmen to strengthen society by a skillful manipulation of the egoistic interests of men. We are naturally disposed, on the other hand, to set ourselves against the public interests when these would suppress egoism and the desire for pleasure. We must therefore choose between morality and culture.—Owing to the fact that this theory apparently supported the doctrine of human depravity and the consequent need of divine revelation, Mandeville fared better at the hands of ecclesiastical polemics than the outspoken pagan, Shaftesbury.
​5. David Hume (1711-1776) brought the critical analysis of the process of human knowledge to a provisional conclusion, especially through his investigation of the two concepts which had played such an important part in the seventeenth-century systems of thought, the concepts of substance and causality. In order to understand the significance of his criticism we must remember that the concepts just named are the presuppositions which are tacitly understood as forming the basis of natural science, of religious thought, and of ordinary conversation. Hume's problem strikes at the root of all human thought. He stated a problem which still continues to bid for solution and of which a final solution is perhaps impossible. Hume is a past master in stating problems. With this he likewise combines a profound psychological talent which enables him, when considering the actual evolution of ideas, to throw light on those points also in which their objective validity remains problematical. This twofold gift is valuable to Hume both in the investigation of the problem of knowledge, as well as in the investigation of the problems of ethics and religion.
Hume was the son of a landlord in southern Scotland. His zeal and aptness for learning and reflection showed themselves at an early age. After several vain attempts to enter some practical vocation he withdrew into retirement and wrote his chief work, the Treatise on Human Nature, during a residence in France (1739-1740). A little later he devoted himself to historical and economic investigations and wrote a history of England, one of the first historical works which takes account of every phase of cultural evolution. His Essays (1748 ff.), besides important treatises on economic subjects, include ​two monographs (Enquiry Concerning Human Understanding and Enquiry Concerning the Principles of Morals) in which the most important problems of his masterpiece are presented in briefer form. He treats the problems of religion from the historico-psychological viewpoint in his Natural History of Religion (1757). The Dialogues on Natural Religion, written in 1751, but not published until after his death, are a critical study of the problem of religion. After having held several public offices, Hume spent his last years at Edinboro in scholarly retirement.
Whilst Locke made a sharp distinction between the problem concerning the origin of our ideas and that of their validity, for Hume the two problems, so far as they pertain to ideas in the more restricted sense (ideas as distinguished from perceptions or impressions, i. e. sensations), are identical. He starts with the assumption that an idea can be valid only when it is based on a sensation (perception, impression). He makes no investigation into the origin of sensations because this problem has no epistemological significance: the question whether they proceed from external objects or from God or from the innate powers of the mind has no bearing on the problem of their validity. Hume likewise excludes that division of knowledge which is wholly confined to the matter of defining and developing the relations of our ideas—pure logic and mathematics—from his critical investigations entirely. The sole problem of his investigations pertains to the validity of the ideas by means of which we presume to be justified in assuming knowledge beyond what is given in sense-perceptions. The problem growing out of the application of mathematics to empirical science was not formulated until later. This was done by Kant on the basis of his studies of Newton.
​The concept of substance (both in its broader and narrow significance) transcends all sense-perception. We never sense anything beyond single attributes in varying degrees of relationship to each other; but things or substances are never sensed. We sense color, hardness,tone, &c., but sensation never gives us anything possessing these attributes. We perceive within ourselves a multitude of ever-varying sensations, ideas and feelings, but we never sense a soul or an Ego. That is to say we never discover a constant element which is always present and to which we are justified in ascribing the name Ego. The concept of causality presents a similar case. We perceive distinct phenomena succeeding each other in time; but we do not sense any internal nexus, any necessary connection. Causality is not an object of experience or of perception. (Hume regards the concepts of experience and perception as identical.) It is impossible in this instance to appeal to immediate certainty (intuition), for such procedure is permissible only in cases where the simple relation of equality and inequality can be shown to apply. It is just as impossible, furthermore, to demonstrate causality by the method of inference, for all phenomena and occurrences become matters of experience in the form of independent facts, and it is never possible to infer from the concept of the given fact that the concept of another fact necessarily follows. The motion of a ball, e. g., is something altogether different from the motion of another ball; the one motion can very readily be conceived without the other. The same method of argument applies to the concept of being as to the concepts of substance and causality; no single sensation ever gives us the concept. To take thought about something and to think of it as ​existing are not two distinct processes. Things acquire no new attribute by our thinking of them as existent.
b. We nevertheless employ all these concepts—substance or thing, cause, being! Hume undertakes to explain how this happens, by means of three distinct psychological factors.—Consciousness naturally tends to continue the processes which have been produced by an intense impression even after the impression ceases. The faculty of imagination continues to be active even though experience is unable to follow. This gives rise to ideal representations, e. g. representations of perfect similarity and perfectly accurate figures, whilst experience only furnishes suggestions and degrees of approach towards the perfect. This is likewise the way in which the representations of absolute substances and absolute being are formed. The faculty of imagination expands the relative constancy which we perceive, into absolute constancy.
Another peculiarity of consciousness is the tendency to combine representations which have frequently been experienced together. When anything happens we are accustomed to find that something else either precedes or follows it; hence, when anything occurs, we expect to find a "cause" and an "effect." But this is nothing more than a habit which has become instinctive. It is impossible to establish the validity" of the causal concept on this basis. This principle of association, which gives rise to this habit, is likewise an example of causality and just for this very reason Hume says, it, too, is inexplicable. Observation never discovers more than the separate elements of the content of consciousness, never any "uniting principle, principle of connection." The problem of explaining the permanent connection of these elements, ​which are absolutely distinct, Hume says, is a difficulty which transcends the powers of my understanding.
Consciousness, in the third place, tends to regard its own states as external, objective phenomena. This is the reason for our regarding sensory qualities as objective attributes. And this is why we regard the mental impulse to pass from a sensation to an idea associated with it as due to an objective necessity. We are here guided by instinct, not by reason.—The foundation of science is belief, not knowledge. And the construction of this foundation takes place, as we have seen, by virtue of the expansive, the associative and the objectifying tendencies of consciousness.
c. Hume did not confine himself to the psychology of knowledge. He has likewise treated the psychology of the passions with the same degree of thoroughness. His exposition in many respects reminds us of Spinoza, He attaches great importance to the manner in which a passion may be combined with another passion by means of the association of the ideas of their respective objects. He asserts, furthermore, that a passion can only be inhibited by another passion, not by pure reason. Reason is the faculty of comparison and reflection and it can only affect the course of the passions indirectly.
Hume's psychology of the passions forms the basis of his ethics. In ethics he sympathizes with the school of Shaftesbury and Hutcheson.—Reason cannot furnish the basis of ethics because it establishes only relations or facts. But good and evil are qualities which are ascribed to human actions and characters according to their effect upon the feelings. The fact that we call actions and characters good which are of no benefit to us proves that the passion which forms the basis of approbation ​cannot be regarded as selfish. In cases of approbation or reproach our viewpoint is social rather than private. If, e. g., we regard justice as a good attribute, it must be due to the fact that we take a sympathetic attitude towards human life as a whole. It may perhaps be that we at first admire justice solely on account of interest in our own security; but this does not furnish the motive for the appreciation of justice in all those cases which bear no relation to our private welfare. Sympathy or fellow- feeling is therefore the fundamental motive of ethical evaluation;
Hume likewise opposes the intellectualistic conception in the philosophy of religion, just as he does in ethics. He instituted a twofold investigation into the problem of knowledge and he likewise follows the same plan in the matter of religion; i. e. he investigates both the psychological origin of religion and the validity of religious ideas.
Religion does not originate from purely intellectual motives, but from fear and hope, and from the disposition to think of all other beings after human analogy. Primitive man represents the beings to which he takes refuge in the fearful moments of his life in very imperfect form. But the native disposition to expand and idealize is also in evidence here, and man gradually recognizes that his God must be an infinite being and that there can be but one God. Parallel with this idealizing tendency, which has the effect of elevating Deity far above anything human and placing Him at a great distance from the finite world, there is another counter tendency which endeavors to represent Deity as near at hand, present and intuitively perceivable, and religion reveals a constant tendency to oscillate between these two extremes. ​
Hume investigates the validity of religious ideas in his Dialogues, which is a very important document in the philosophy of religion of the modern period. He adduces several different viewpoints: that of a speculative Supernaturalist, a rationalistic Deist and a skeptical Naturalist. Although the naturalist finally courteously withdraws, it is neverthless clear that Hume regarded his arguments as the most important and most conclusive. He denies the right to infer the existence of God from the order and teleology of the universe: Why could the teleology (so far as it really exists!) not have arisen from natural causes and gradual adaptation? We explain the particular phenomena of nature by referring them to natural causes, and the whole series is explained in the explanation of its several parts. At any rate it is impossible to infer, from a world which reveals so many imperfections together with its teleology, the existence of an absolutely perfect being. Furthermore, if we should wish to attribute the origin of the universe to a divine idea, we must not forget that this idea is nowhere given in experience except as a phenomenon combined with other phenomena: with what right, therefore can we deduce all the other parts from this single part?— If the naturalist still gets no farther than to discover difficulties in each of the various viewpoints, it is certainly not enough that we regard it merely as a matter of caution, but rather as the expression of Hume's constant effort to state the problems clearly and to keep them open.
6. Hume's clear statement of the problem of knowledge did not call forth any profound reply immediately. England has not even furnished such a reply.—On the contrary the English literature of the latter half of the 18th century consists of a series of philosophic efforts ​which in part continue and supplement and in part oppose Hume.
Adam Smith (1723-1790), a professor at Glasgow and a friend of Hume, elaborated his ethical theory more fully. In his Theory of Moral Sentiments(1759) he describes the moral sense in its evolution from the mere instinct of sympathy. A spontaneous impulse of imitation causes us to put ourselves in the place of others, and our feelings and judgments are therefore primarily determined by environment. But, on the other hand, if the feelings and judgments of others are not of the same kind and intensity as those which arise in our own minds in their stead, or would naturally arise, we then experience a feeling of disapprobation. Again, we approve their feelings and their judgments (as well as their conduct) whenever, according to our own experience, they seem to stand in a fitting relation to the causes which give rise to them,— and whenever our sympathy for them, for the objects of their judgments and conduct, is not abnormal. To illustrate, we cease to approve of acts of revenge whenever the revenge seems to be too cruel for the circumstances and the subject. A standard is thus gradually evolved which is wholly free from any reference to utility. And we likewise apply this standard to ourselves. We discover that we are criticized by others and not only criticizing others ourselves. We divide ourselves, so to speak, into two persons, of whom the one criticizes the other in the capacity of an impartial witness. We unconsciously idealize this witness; that is we ascribe to him a far more comprehensive knowledge than it is possible for man to attain.
It has frequently been observed that Smith's ethics radically contradicts his famous work in economics, ​The Wealth of Nations (1776). But, on the other hand, the fact that both works were originally parts of one and the same course of lectures does not harmonize with this view. Moreover the fact has been overlooked, that in his political economy Smith assumes the attitude of an "impartial witness" of industrial life: his demand for unconditional liberty in commerce and industry rests upon the principle that this is the only way in which capacity can be properly developed and the best methods and instruments of production and of trading be discovered. It frequently happens that the individual serves the community best when he is most concerned about his own interests; he, at the same time, serves a purpose which he has not proposed as if guided by an unseen hand. Sympathy with human life in every phase forms the basis of Smith's political economy; it covers the effort of laborers to secure better wages, as well as the effort of employers to increase production. His ethics is therefore in internal harmony with his economics. It is admitted, as a matter of course, that he did not fully appreciate the social problem in its entire scope. His contention was directed against the trusteeship of the reactionary governments, and his optimism led him to expect a large measure of social harmony, even a harmony between ethics and economics, if we should only permit evolution to have free course.
The association of ideas had a profound influence on Hume's theory of knowledge. The physician, David Hartley(1705-1757), supplemented his theory on this point. He endeavored to explain all the higher mental phenomena by means of the association of simple sensations and ideas. According to Hartley, the laws of association are the highest spiritual laws of nature ​(Observation on Man, 1749). The physiological correlate of association is the combination of various oscillations of particles of the brain. The significance of association manifests itself in three specific forms: it is possible for ideas to so unite internally as to form a new idea with new attributes; conscious activities may, by repetition, be performed entirely automatically; the vividness of an idea may be transferred to the idea which is associated with it. Consciousness can assume an entirely different character from its original by means of these three processes. The most radical metamorphoses become possible in this way, as e. g. when an egoist lapses into complete mystical self-forgetfulness through a series of degrees.—These theories were popularized through the writings of Joseph Priestley(1733-1804), the noted chemist. And Erasmus Darwin(1731-1802) afterwards went a step farther, and proposed the hypothesis of the transmissibility of such acquired characters (Zoonomia, 1794).
Hume was opposed by what has been called, in the narrower sense, the Scottish School. These thinkers aim to quit theorizing and return to the mere description of mental phenomena. As against the results of analytical philosophy they appeal to common sense. Thomas Reid(1710-1796), Professor at Aberdeen and Glasgow, is the most famous representative of this school. His most important work, Inquiry into the Human Mind on the Principles of Common Sense(1764), was written against Hume, whom he regarded as the destroyer of all science, religion and virtue.
According to Reid, there are certain instinctive presuppositions at the basis of all knowledge, which are unassailable by doubt. These principles of common sense are older than philosophy and proceed from the ​hand of God. Thus, e. g. every sensation by natural suggestion gives rise to the belief in an external object, as also in an ego as the subject of the sensation. In this way the causal instinct also leads us to the presupposition that the combinations of phenomena which we have perceived will likewise take place in the same way in the future. We likewise have such intuitive evidence in the sphere of morals; we judge a given act good, another evil, intuitively and spontaneously.—Reid overlooked the fact that Hume had expressly recognized common sense; but Hume discovered a profound problem in case one should wish to investigate the foundation of common sense. Kant afterwards remarked very pertinently, that instead of making use of common sense as authority, it should rather be used in refutation of objections.