In the melodramatic fashion so common in what is called philosophy we may delight ourselves with such flashes of lightning as this: _esse est percipi_. The truth of this paradox lies in the fact that through perception alone can we get at being—a modest and familiar notion which makes, as Plato’s “Theætetus” shows, not a bad point of departure for a serious theory of knowledge. The sophistical intent of it, however, is to deny our right to make a distinction which in fact we do make and which the speaker himself is making as he utters the phrase; for he would not be so proud of himself if he thought he was thundering a tautology. If a thing were never perceived, or inferred from perception, we should indeed never know that it existed; but once perceived or inferred it may be more conducive to comprehension and practical competence to regard it as existing independently of our perception; and our ability to make this supposition is registered in the difference between the two words _to be_ and _to be perceived_—words which are by no means synonymous but designate two very different relations of things in thought. Such idealism at one fell swoop, through a collapse of assertive intellect and a withdrawal of reason into self-consciousness, has the puzzling character of any clever pun, that suspends the fancy between two incompatible but irresistible meanings. The art of such sophistry is to choose for an axiom some ambiguous phrase which taken in one sense is a truism and taken in another is an absurdity; and then, by showing the truth of that truism, to give out that the absurdity has also been proved. It is a truism to say that I am the only seat or locus of my ideas, and that whatever I know is known by me; it is an absurdity to say that I am the only object of my thought and perception. [Sidenote: Reality is the practical made intelligible.] To confuse the instrument with its function and the operation with its meaning has been a persistent foible in modern philosophy. It could thus come about that the function of intelligence should be altogether misconceived and in consequence denied, when it was discovered that figments of reason could never become elements of sense but must always remain, as of course they should, ideal and regulative objects, and therefore objects to which a practical and energetic intellect will tend to give the name of realities. Matter is a reality to the practical intellect because it is a necessary and ideal term in the mastery of experience; while negligible sensations, like dreams, are called illusions by the same authority because, though actual enough while they last, they have no sustained function and no right to practical dominion.