The image of a stone formed in our minds is no representation of the object which has given rise to it.  Not only, as has been often remarked, is there no resemblance between the particular thought and the particular thing, but thoughts and things generally are too unlike to be compared.  An idea of a stone may be like an idea of another stone, or two stones may be like one another; but an idea of a stone is not like a stone; it cannot be thrown at anything, it occupies no room in space, has no specific gravity, and when we come to know more about stones, we find our ideas concerning them to be but rude, epitomised, and highly conventional renderings of the actual facts, mere hieroglyphics, in fact, or, as it were, counters or bank-notes, which serve to express and to convey commodities with which they have no pretence of analogy.

Indeed we daily find that, as the range of our perceptions becomes enlarged either by invention of new appliances or after use of old ones, we change our ideas though we have no reason to think that the thing about which we are thinking has changed.  In the case of a stone, for instance, the rude, unassisted, uneducated senses see it as above all things motionless, whereas assisted and trained ideas concerning it represent motion as its most essential characteristic; but the stone has not changed.  So, again, the uneducated idea represents it as above all things mindless, and is as little able to see mind in connection with it as it lately was to see motion; it will be no greater change of opinion than we have most of us undergone already if we come presently to see it as no less full of elementary mind than of elementary motion, but the stone will not have changed.

The fact that we modify our opinions suggests that our ideas are formed not so much in involuntary self-adjusting mimetic correspondence with the objects that we believe to give rise to them, as by what was in the outset voluntary, conventional arrangement in whatever way we found convenient, of sensation and perception-symbols, which had nothing whatever to do with the objects, and were simply caught hold of as the only things we could grasp.  It would seem as if, in the first instance, we must have arbitrarily attached some one of the few and vague sensations which we could alone at first command, to certain motions of outside things as echoed by our brain, and used them to think and feel the things with, so as to docket them, and recognise them with greater force, certainty, and clearness—­much as we use words to help us to docket and grasp our feelings and thoughts, or written characters to help us to docket and grasp our words.