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.
