These principles, having thus been established by science, are available for direction in the arts. The physician acts under their guidance; and his object is simply to regulate his treatment and advice in accordance with them. In other words, _he endeavours to imitate Nature_, to remove the obstructions which he finds interfering with her operations, or to lend that aid which a knowledge of these principles points out as necessary. The surgeon and the dentist follow the same course, but more directly. In healing a wound, for example, the surgeon has to ascertain from science how Nature in similar cases proceeds when left to herself; and all his cuttings, and lancings, and dressings, are nothing more than _attempts to imitate her_ in her healing operations. So well is this now understood, that every operation which does not at least recognise the principle is denounced--and justly denounced--as quackery; and the reason is, that uniform experience has convinced professional men, that they can only expect success when they follow with docility in the path which Nature has pointed out to them. Precisely similar should be the plan of operation pursued by the Educationist. He should, in the first place, take a comprehensive view of the whole subject, and endeavour to map out to himself its great natural divisions;--in other words, he should endeavour to ascertain what are the things which Nature teaches, that he may, by means of this great outline, form a general programme for the direction of the teacher. His next object ought to be, to ascertain the mode, and the means, adopted by Nature in forwarding these several departments of her educational process; the powers of mind engrossed in each; the order in which they are brought into exercise; and the combinations which she employs in perfecting them. In ascertaining these principles which regulate the operations of Nature in her educational processes, the same adherence to the rules prescribed by the inductive philosophy, which has crowned the other sciences with success, must be rigidly observed. There must be the same disregard of mere antiquity; there must be the same scrupulous sifting of evidence, and strict adherence to facts; there must be a discarding of all hypotheses, and a simple dependence upon ascertained truths alone. Adherence to these rules is as necessary in cultivating the science of education, as it has been in the other sciences; and the neglect of any one of them, may introduce an element of error, which may injure the labours of a whole lifetime.