Further: man's senses are constituted with an adaptation to the external world; and his intellectual constitution is adapted to intercourse with his fellow man. The delicate bony structure of the ear, which conveys sounds from the tympanum to the sensorium, is nicely adjusted by the Maker to appreciate and convey the tones and modulations of the human voice. Human gesture, likewise, and the expression of the countenance and the eye, are auxiliary to human language in conveying instruction. The nature of man, therefore, is adapted, both physically and intellectually, to receive knowledge by communications from one of his own species. If God designed that an angel should instruct the human family, one of two things would have to be done--either the human constitution would have to be elevated and adapted to intercourse with a being of a higher order in the scale of creation, or that being would have to let down his nature to human capacity, and thus adapt himself to intercourse with human natures. And it would even be requisite that the teacher should not assume the highest condition of humanity in order that his instructions should accomplish the greatest general good; nor should his communications be made in the most cultivated and elevated style of language. If he would instruct the common mind in the best manner, he must use common language and common illustrations; and if God (blessed be his name) were himself to instruct human nature, _as it is_, the same means would be necessary. Another step--Man is so constituted that he learns by example better than precept. Theory without practice, or precept without example, does not constitute a perfect system of instruction. The theory of surveying, however perfect it may be taught in college, never makes a practical surveyor. An artist may give a most perfect theory of his art to his apprentices or those whom he wishes to instruct in a knowledge of his business; but if he would have them become practical artists themselves, he must, with tools in hand, practise his own instructions before the eyes of the learner. In the language of the trades, he must 'show how it's done.' Such, then, is the nature of man, that in order to a perfect system of instruction there must be both precept and example.