=Locke’s Work and Its Various Classifications.=--Because of their relation to an important topic in modern education, the theories of John Locke (1632-1704) should receive further attention than they have yet been given. No writer on education has been more variously classified than he. We have already seen (p. 154) that the general tenor of his _Thoughts concerning Education_ would lead us to group him with the early realistic movement. There are also elements in this work that would seem to place him with the sense realists, and many of his ideas proved so similar and suggestive to Rousseau’s thought (see p. 213), that he has sometimes been classed among the advocates of naturalism. But Locke’s _Thoughts_, by which his educational position is often exclusively judged, were simply a set of practical suggestions for the education of a gentleman, written for a friend as advice in bringing up his son. They make clear his general sympathy with the current educational reform, but do not bring out his main point of view. His central thought appears more definitely through the philosophical principles in his famous _Essay concerning the Human Understanding_, and through the intellectual training suggested in his other educational work, _Conduct of the Understanding_, which was originally an additional book and application of the _Essay_. [Sidenote: But his underlying thought is ‘discipline’.] [Sidenote: To train the mind, mathematics and a range of sciences should be studied.] =Locke’s Disciplinary Theory in Intellectual Education.=--Probably Locke’s underlying thought as to the proper method of intellectual, moral, and physical training may best be summed up in the word ‘discipline.’ This educational attitude is a natural corollary of his philosophic position. In his _Essay_ he holds that ideas are not born in one, but that all knowledge comes from experience. The mind, he declares, is like ‘white paper, or wax,’ upon which impressions from the outside world are made through our senses. When the ideas are once in mind, it is necessary to determine what they tell us in the way of truth. Hence, to train the mind to make proper discriminations, he declares in the _Conduct of the Understanding_ that practice and discipline are necessary. “Would you have a man reason well, you must use him to it betimes, exercise his mind in observing the connection of ideas and following them in train.” As to the means of effecting this mental discipline, Locke holds: “Nothing does this better than mathematics, which therefore I think should be taught all those who have the time and opportunity, not so much to make them mathematicians as to make them reasonable creatures, that having got the way of reasoning, which that study necessarily brings the mind to, they might be able to transfer it to other parts of knowledge as they shall have occasion.” Similarly, he advises a wide range of sciences, “to accustom