For just as an artist cannot draw the portrait of an individual in such fashion that he could be certain of having done a proper job unless he had a distinct idea of the individual, and indeed unless the subject were to sit for it so a mind that, for example, has only the idea of being or of animal in general cannot represent a horse to itself, or form a vecy distinct idea of it, or be sure that the idea exactly resembles a horse, unless it already has an initial idea against which it compares the second.