Part 6 — CHAPTER XII, section 48. The notes to Chapter III (see above) are in point here. It is well worth the student's while to read the whole of Chapter XI, Book IV, of Locke's "Essay." It is entitled "Of our Knowledge of the Existence of Other Things." Notice the headings of some of his sections:—

Section 1. "It is to be had only by sensation."

Section 2. "Instance whiteness of this paper."

Section 3. "This, though not so certain as demonstration, yet may be called 'Knowledge,' and proves the existence of things without us."

Locke's argument proceeds, as we have seen, on the assumption that we perceive external things directly,—an assumption into which he slips unawares,—and yet he cannot allow that we really do perceive directly what is external. This makes him uncomfortably conscious that he has not absolute proof, after all. The section that closes the discussion is entitled: "Folly to expect demonstration in everything."

Section 49. I wish that I could believe that every one of my readers would sometime give himself the pleasure of reading through Berkeley's "Principles of Human Knowledge" and his "Three Dialogues between Hylas and Philonous." Clearness of thought, beauty of style, and elevation of sentiment characterize them throughout.

The "Principles" is a systematic treatise. If one has not time to read it all, one can get a good idea of the doctrine by running through the first forty-one sections. For brief readings in class, to illustrate Berkeley's reasoning, one may take sections 1-3, 14, 18-20, and 38.

The "Dialogues" is a more popular work. As the etymology of the names in the title suggests, we have in it a dispute between a man who pins his faith to matter and an idealist. The aim of the book is to confute skeptics and atheists from the standpoint of idealism.

For Hume's treatment of the external world, see his "Treatise of Human Nature," Part IV, section 2. For his treatment of the mind, see Part IV, section 6.