The following passage on what may be called the associations of antipathy affords a good instance of Locke's power of homely and apposite illustration: "Many children imputing the pain they endured at school to their books they were corrected for, so join those ideas together, that a book becomes their aversion, and they are never reconciled to the study and use of them all their lives after; and thus reading becomes a torment to them, which otherwise possibly they might have made the great pleasure of their lives. There are rooms convenient enough, that some men cannot study in, and fashions of vessels, which though never so clean and commodious, they cannot drink out of, and that by reason of some accidental ideas which are annexed to them and make them offensive. And who is there that hath not observed some man to flag at the appearance or in the company of some certain person not otherwise superior to him, but because, having once on some occasion got the ascendant, the idea of authority and distance goes along with that of the person, and he that has been thus subjected is not able to separate them." Had Locke's _Essay_ ended with the Second Book, we should hardly have detected in it any incompleteness. It might have been regarded as an analytical work on the nature and origin of our ideas, or, in other words, on the elements of our knowledge. There are, however, a third and fourth book--the former treating "Of Words," the latter "Of Knowledge and Opinion." Locke's notion appears to have been that, after treating of "Ideas," mainly as regarded in themselves, it was desirable to consider them as combined in Judgments or Propositions, and to estimate the various degrees of assent which we give or ought to give to such judgments, when formed. The Fourth Book thus, to a certain extent, takes the place, and was probably designed to take the place, of the Logic of the Schools. "But," to quote Locke's own language in the Abstract of the _Essay_, "when I came a little nearer to consider the nature and manner of human knowledge, I found it had so much to do with propositions, and that words, either by custom or necessity, were so mixed with it, that it was impossible to discourse of knowledge with that clearness we should, without saying something first of words and language." The last three Chapters of the Third Book are remarkable for their sound sense, and may still be read with the greatest advantage by all who wish to be put on their guard against the delusions produced by misleading or inadequate language--those "Idola Fori" which Bacon describes as the most troublesome of the phantoms which beset the mind in its search for truth. Some of the best and freshest of Locke's thoughts, indeed, are to be found in this book, and especially in the less technical parts of it.