And it should be noted that this peculiar ambiguity in the names of things entails a parallel ambiguity in the use of the words by which we indicate the mind's recognition of the presence of things. We commonly speak of a drunken man's _seeing_ two trees, where a sober man sees one. We speak of an insane man as _hearing_ voices, when no one has spoken. We say that we _see_ the maples are turning red, even when we believe that color may not properly be attributed to the mediate object of knowledge. On the other hand, those who hold to the existence of "real" objects of the kind before mentioned, generally maintain that in referring to things in space, their positions and mutual relations, we are giving attention, not to the immediately known, but to its "external" double. "I see, feel, perceive," it is "said, not the image, and not the constituents of the image (the ideas), but the external object by _means_ of the image."[5] If one holds that this "external" object presupposes a substance, a something distinct from a group of qualities, there is nothing to prevent his maintaining, should he wish to do so, that in saying "I see a tree," primary reference is had to this substance or "reality." Of course, if, in the sentence "I see a tree," the word "tree" can have three meanings, it follows that there is also a possibility of taking in three senses the word "see." It is hardly necessary to point out that, unless one is very careful, "seeing" in one sense may result in "believing" in another, as "kicking" did in the famous case of Dr. Johnson and the stone. The caution is pertinent with respect to any other word used in the same general way as we use the word "see." [5] Ueberweg. See Krauth's Ed. of Berkeley's "Principles," Phila., 1874, p. 343. I have said that when a man abandons his original unreflective position and learns to distinguish between things immediately known and other things they are supposed to represent, he goes on using the common language, and talking as though there were but one thing under consideration. Now, men do not do this merely in common conversation and in writing about matters of everyday life, but they do it in the very books that have been written to prove that each thing is thus double or triple. John Locke, for example, begins the very chapter in which he is about to draw the distinction between the secondary and primary qualities of bodies (_i. e._, between the constituents of things immediately known and the constituents of their "external" correlates), as well as to enlighten us on our ideas of substances, with the following words:[6] [6] "Essay", Bk. 2, Chap. 23, § 1.