It is of great importance to observe, that these faculties of receiving ideas, retaining them, and compounding them, are among the many things of which we can give no explanation. These invisible springs of our being are of nature's workmanship, and not of our own. Perhaps this gift of God, imagination, is the sole instrument with which we compound ideas, even those which are abstract and metaphysical. You pronounce the word "triangle;" but you merely utter a sound, if you do not represent to yourself the image of some particular triangle. You certainly have no idea of a triangle but in consequence of having seen triangles, if you have the gift of sight, or of having felt them, if you are blind. You cannot think of a triangle in general, unless your imagination figures to itself, at least in a confused way, some particular triangle. You calculate; but it is necessary that you should represent to yourself units added to each other, or your mind will be totally insensible to the operation of your hand. You utter the abstract terms--greatness, truth, justice, finite, infinite; but is the term "greatness" thus uttered, anything more or less, than a mere sound, from the action of your tongue, producing vibrations in the air, unless you have the image of some greatness in your mind? What meaning is there in the words "truth" and "falsehood," if you have not perceived, by means of your senses, that some particular thing which you were told existed, did exist in fact; and that another of which you were told the same, did not exist? And, is it not from this experience, that you frame the general idea of truth and falsehood? And, when asked what you mean by these words, can you help figuring to yourself some sensible image, occasioning you to recollect that you have sometimes been told, as a fact, what really and truly happened, and very often what was not so? Have you any other notion of just and unjust, than what is derived from particular actions, which appeared to you respectively of these descriptions? You began in your childhood by learning to read under some master: you endeavored to spell well, but you really spelled ill: your master chastised you: this appeared to you very unjust. You have observed a laborer refused his wages, and innumerable instances of the like nature. Is the abstract idea of just and unjust anything more than facts of this character confusedly mixed up in your imagination?