# The Great Didactic of John Amos Comenius/The Great Didactic/Chapter 20

CHAPTER XX
THE METHOD OF THE SCIENCES, SPECIFICALLY
1. We must now collect together the scattered observations that we have made on the proper teaching of the sciences, of the arts, of morality, and of piety. By proper teaching I mean teaching that combines ease, thoroughness, and rapidity.
2. Science, or the knowledge of nature, consists of an internal perception, and needs the same accessories as the external perception of the eye, namely, an object to observe, and light by which to observe it. If these be given, perception will follow. The eye of the inner perception is the mind or the understanding, the object is all that lies within or without our apprehension, while the light is the necessary attention. But, as in the case of external perception a definite procedure is necessary in order to apprehend things as they are, so with internal perception a certain method is necessary if things are to be presented to the mind in such a way that it can grasp them and assimilate them with ease.
3. The youth who wishes to penetrate the mysteries of the sciences must carefully observe four rules:
(iv)(i) He must keep the eye of his mind pure.
(iv)(ii) He must see that the object be brought near to it.
(iv)(iii) He must pay attention.
(iv) He must proceed from one object to another in ​accordance with a suitable method. For thus he will apprehend everything surely and easily.
4. Over the amount of ability that we possess we have no control, for God has portioned out this mirror of the understanding, this inner eye, according to His will. But it lies in our power to prevent it from growing dusty or dim. By dust, I mean the idle, useless, and empty occupations of the mind. For our mind is in constant activity, like a continually running mill-stone, and is supplied by its servants, the external senses, with material from every side. But unless the chief inspector, the on, be continually on the watch, worthless material is supplied, such as chaff, straw, or sand, instead of corn or wheat. Thus it comes to pass that, as in the case of a mill, every corner is filled with dust. This inner mill, therefore, the mind (which is also a mirror) will be kept free from dust, if the young be kept away from worthless occupations and be skilfully trained to like worthy and useful things.
5. In order that the mirror may duly receive the images of the objects, it is necessary that these latter be solid and visible, and be also placed suitably before the eyes. Clouds and similar objects that possess little consistency make but a slight impression on a mirror, while objects that are not present make none at all. Those things, therefore, that are placed before the intelligence of the young, must be real things and not the shadows of things. I repeat, they must be things; and by the term I mean determinate, real, and useful things that can make an impression on the senses and on the imagination. But they can only make this impression when brought sufficiently near.
6. From this a golden rule for teachers may be derived. Everything should, as far as is possible, be placed before the senses. Everything visible should be brought before the organ of sight, everything audible before that of hearing. Odours should be placed before the sense of smell, and things that are tastable and tangible before the sense of taste and of touch respectively. If an object can make ​an impression on several senses at once, it should be brought into contact with several, though with the limitations imposed in the seventh Principle of chap. viii.
7. For this there are three cogent reasons. Firstly, the commencement of knowledge must always come from the senses (for the understanding possesses nothing that it has not first derived from the senses). Surely, then, the beginning of wisdom should consist, not in the mere learning the names of things, but in the actual perception of the things themselves! It is when the thing has been grasped by the senses that language should fulfil its function of explaining it still further.
8. Secondly, the truth and certainty of science depend more on the witness of the senses than on anything else. For things impress themselves directly on the senses, but on the understanding only mediately and through the senses. This is evident from the fact that belief is at once accorded to knowledge derived from the senses, while an appeal is always made to them from a priori reasoning and from the testimony of others. We do not trust a conclusion derived from reasoning unless it can be verified by a display of examples (the trustworthiness of which depends on sensuous perception). No one could have such confidence in the testimony of another person as to disbelieve the experience of his own senses. Science, then, increases in certainty in proportion as it depends on sensuous perception. It follows, therefore, that if we wish to implant a true and certain knowledge of things in our pupils, we must take especial care that everything be learned by means of actual observation and sensuous perception.
9. Thirdly, since the senses are the most trusty servants of the memory, this method of sensuous perception, if universally applied, will lead to the permanent retention of knowledge that has once been acquired. For instance, if I have once tasted sugar, seen a camel, heard a nightingale sing, or been in Rome, and have on each occasion attentively impressed the fact on my memory, the incidents will ​remain fresh and permanent. We find, accordingly, that children can easily learn Scriptural and secular stories from pictures. Indeed, he who has once seen a rhinoceros (even in a picture) or been present at a certain occurrence, can picture the animal to himself and retain the event in his memory with greater ease than if they had been described to him six hundred times. Hence the saying of Plautus: “An eye-witness is worth more than ten ear-witnesses.” Horace also says: “What is entrusted to the fickle ears makes less impression on the mind than things which are actually presented to the eyes and which the spectator stores up for himself.”
In the same manner, whoever has once seen a dissection of the human body will understand and remember the relative position of its parts with far greater certainty than if he had read the most exhaustive treatises on anatomy, but had never actually seen a dissection performed. Hence the saying, “Seeing is believing.”
10. If the objects themselves cannot be procured, representations of them may be used. Copies or models may be constructed for teaching purposes, and the same principle may be adopted by botanists, geometricians, zoologists, and geographers, who should illustrate their descriptions by engravings of the objects described. The same thing should be done in books on physics and elsewhere. For example, the human body will be well explained by ocular demonstration if the following plan be adopted. A skeleton should be procured (either such an one as is usually kept in universities, or one made of wood), and on this framework should be placed the muscles, sinews, nerves, veins, arteries, as well as the intestines, the lungs, the heart, the diaphragm, and the liver. These should be made of leather and stuffed with wool, and should be of the right size and in the right place, while on each organ should be written its name and its function. If you take the student of medicine to this construction and explain each part to him separately, he will grasp all the details without any effort, and from that time forth will ​understand the mechanism of his own body. For every branch of knowledge similar constructions (that is to say, images of things which cannot be procured in the original) should be made, and should be kept in the schools ready for use. It is true that expense and labour will be necessary to produce these models, but the result will amply reward the effort.
11. If any be uncertain if all things can be placed before the senses in this way, even things spiritual and things absent (things in heaven, or in hell, or beyond the sea), let him remember that all things have been harmoniously arranged by God in such a manner that the higher in the scale of existence can be represented by the lower, the absent by the present, and the invisible by the visible. This can be seen in the Macromicrocosmus of Robert Flutt,$^{30}$ in which the origin of the winds, of rain, and of thunder is described in such a way that the reader can visualise it. Nor is there any doubt that even greater concreteness and ease of demonstration than is here displayed might be attained.
12. So much of the presentation of objects to the senses. We must now speak of the light, the absence of which renders the presentation of objects to the eyes useless. This light of the teaching art is attention, and by its means the learner can keep his mind from wandering and can take in everything that is put before him. It is impossible for any man to see an object in the dark, or if his eyes be closed, no matter how near to him it may be; and in the same way, if you talk to one who is not attending, or show him anything, you will make no impression on his senses. This we can observe in the case of those who, while lost in thought, do not notice what is going on before their eyes. He, therefore, who wishes to show anything to another at night must provide light, and must polish the object so that it shines; and in the same way a master, if he wish to illumine with knowledge a pupil shrouded in the darkness of ignorance, must first excite his attention, that he may drink in information with a greedy mind. ​How this can be done we have shown in the 17th chapter, and in the first Principle of the 19th chapter.
13. So much of the light. We will now speak of the mode in which objects must be presented to the senses, if the impression is to be distinct. This can be readily understood if we consider the processes of actual vision. If the object is to be clearly seen it is necessary: (1) that it be placed before the eyes; (2) not far off, but at a reasonable distance; (3) not on one side, but straight before the eyes; (4) and so that the front of the object be not turned away from, but directed towards, the observer; (5) that the eyes first take in the object as a whole; (6) and then proceed to distinguish the parts; (7) inspecting these in order from the beginning to the end; (8) that attention be paid to each and every part; (9) until they are all grasped by means of their essential attributes. If these requisites be properly observed, vision takes place successfully; but if one be neglected its success is only partial.
14. For instance, if any one wish to read a letter that has been sent him by a friend, it is necessary: (1) that it be presented to the eyes (for if it be not seen, how can it be read?); (2) that it be placed at a suitable distance from the eyes (for if it be too far off, the words cannot be distinguished); (3) that it be directly in front of the eyes (for if it be on one side, it will be confusedly seen); (4) that it be turned the right way up (for if a letter or a book be presented to the eyes upside down or on its side, it cannot be read); (5) the general characteristics of the letter, such as the address, the writer, and the date must be seen first (for unless these facts be known, the particular items of the letter cannot be properly understood); (6) then the remainder of the letter must be read, that nothing be omitted (otherwise the contents will not all be known, and perhaps the most important point will be missed); (7) it must be read in the right order (if one sentence be read here and another there, the sense will be confused); (8) each sentence must be mastered before the next is com​menced (for if the whole be read hurriedly, some useful point may easily escape the mind); (9) finally, when the whole has been carefully perused, the reader may proceed to distinguish between those points that are necessary and those that are superfluous.
15. These points should be observed by those who teach the sciences, and may be expressed in nine very useful precepts.
(i) Whatever is to be known must be taught.
Unless that which is to be known be placed before a pupil, how is he to acquire a knowledge of it? Therefore let those who teach beware of concealing anything from their pupils, whether of intent, do the envious and dishonest, or through carelessness, as is the case with those who perform their duties in a perfunctory manner. The two things necessary are honesty and hard work.
16. (ii) Whatever is taught should be taught as being of practical application in every-day life and of some definite use.
That is to say, the pupil should understand that what he learns is not taken out of some Utopia or borrowed from Platonic Ideas, but is one of the facts which surround us, and that a fitting acquaintance with it will be of great service in life. In this way his energy and his accuracy will be increased.
17. (iii) Whatever is taught should be taught straightforwardly, and not in a complicated manner.
This means that we must look straight at objects and not squint, for in that case the eyes do not see that at which they look, but rather distort and confuse it. Objects should be placed before the eyes of the student in their true character, and not shrouded in words, metaphors, or hyperboles. These devices have their use if the object be to exaggerate or to detract from, to praise or to blame what is already known. But when knowledge is being acquired they should be avoided and the facts should be set forth plainly.
18. (iv) Whatever is taught must be taught with reference ​to its true nature and its origin; that is to say, through its causes.
This method of cognition is the best if the true nature of a fact is to be learned. For if its true nature be not made evident, this is not cognition but error. The true nature of a fact lies in the process that brought it into being. If it appear to contain elements not accounted for by that process, it is evident that there is some misapprehension. Now everything is brought into existence by its causes. Therefore to explain the causes of anything is equivalent to making a true exposition of that thing’s nature, in accordance with the principles: “Knowledge consists in having a firm grip of causes,” and “Causes are the guides of the understanding.” Objects can thus be best, easiest, and most certainly cognised through a knowledge of the processes that produced them. If a man wish to read a letter he holds it as it was written, since it is a difficult thing to read a document that is inverted, or on its side, and in the same way, if a fact be explained by means of the process that gave it birth, it will be easily and surely understood. If, however, the teacher reverse the order of nature, he is certain to confuse the student. Therefore, the method employed in teaching should be based on the method of nature. That which precedes should be taken first, and that which follows last.
19. (v) If anything is to be learned, its general principles must first be explained. Its details may then be considered, and not till then.
The reasons for this have been given in chap. xvi. Principle 6. We give a general notion of an object when we explain it by means of its essential nature and its accidental qualities. The essential nature is unfolded by the questions what? of what kind? and why? Under the question what? are included the name, the genus, the function, and the end. Under the question of what kind? comes the form of the object, or the mode in which it is fitted to its end. Under the question why? the efficient ​or causal force by which an object is made suitable to its end. For example, did I wish to give a student a general notion of a man, I should say: Man is (1) the chief creation of God, and destined for dominion over other creatures; (2) endowed with freedom of choice and action; (3) and on that account provided with the light of reason, that he may direct his choice and his actions with wisdom. This is but a general notion of man, but it goes to the root of the matter and says everything about him that is essential. To these you may, if you like, add some of his accidental qualities, still keeping to generalities, and this must be done by asking the questions from what origin? whence? when? You may then proceed to his parts, the body and the soul. The nature of the body can be demonstrated through the anatomy of its organs; that of the soul by examining the faculties of which it consists. All these points must be taken in their proper order.
20. (vi) All the parts of an object, even the smallest, and without a single exception, must be learned with reference to their order, their position, and their connection with one another.
Nothing exists in vain, and sometimes the strength of the larger parts depends on that of the smallest. Certain it is that in a clock, if one pin be broken or bent, or moved out of its place, the whole machine will stop. Similarly, in a living body, the loss of one organ may cause life to cease, and in a sentence it is often on the smallest words, such as prepositions and conjunctions, that the whole sense depends. Perfect knowledge of an object can therefore only be attained by acquiring a knowledge of the nature and function of each of its parts.
21. (vii) All things must be taught in due succession, and not more than one thing should be taught at one time. The organ of vision is unable to take in two or three objects at one time (certain it is that he who reads a book cannot look at two pages at once, nay, cannot even see two lines, though they lie quite close together, nor two words, nor two letters, otherwise than successively); and in the ​same way the mind can only grasp one thing at a time. We should therefore make a distinct break in our progress from one thing to another, that we may not overburden the mind.
22. (viii) We should not leave any subject until it is thoroughly understood.
Nothing can be done in a moment. For every process involves motion, and motion implies successive stages. The pupil should therefore not pass on from any point in a science until he has thoroughly mastered it and is conscious that he has done so. The methods to be employed are emphatic teaching, examination, and iteration, until the desired result is attained. This we have pointed out in chap. xviii. Principle 10.
23. (ix) Stress should be laid on the differences which exist between things, in order that what knowledge of them is acquired may be clear and distinct.
Much meaning lies concealed in that celebrated saying: “He who distinguishes well is a good teacher.” For too many facts overwhelm a student, and too great a variety confuses him. Remedies must therefore be applied: in the first case order, by means of which one thing may be taken after another; in the second, a careful consideration of the differences that exist in nature, that it may always be evident in what respects one thing differs from another. This is the only method that can give distinct, clear, and certain knowledge; since the variety and actuality of natural objects depend on their distinctive attributes, as we have hinted in chap. xviii. Principle 6.
24. Now it is impossible that all teachers, when they enter on their profession, should be possessed of the requisite skill, and it is therefore necessary that the sciences which are taught in schools be mapped out in accordance with the foregoing laws. If this be done it will be difficult for any teacher to miss his mark. For, if the laws be rigorously observed, it is beyond question that any man who is once admitted into the royal palace and is allotted a certain space of time can easily and without any trouble ​master its whole contents, its pictures, statues, carpets, and other ornaments; and just as easy will it be for a youth who is admitted to the theatre of this world to penetrate with his mental vision the secrets of nature, and from that time forward to move among the works of God and of man with his eyes opened.