This property of the understanding, by which certain judgments, naturally follow certain perceptions, and are followed by other judgments, is the faculty of reason, of order and proportion in the mind, and is indeed nothing but the understanding acting by rule or necessity. The long controversy between Locke and Leibnitz with respect to innate ideas turned upon the distinction here stated, innate ideas being thus referred not to the actual impressions of objects, but to the forms or moulds existing in the mind, and in which those impressions are cast. Leibnitz contended that there was a germ or principle of truth, a pre-established harmony between its innate faculties and its acquired ideas, implied in the essence of the mind itself. According to the one it was like a piece of free stone, which the mason hews with equal ease in all directions, and into any shape, as circumstances require: according to the other, it resembles a piece of marble strongly ingrained, with the figure of a man, or other animal, inclosed in it, and which the sculptor has only to separate from the surrounding mass. I will add one more passage to draw the attention of my readers to this intricate subject, and to show that the difficulties surrounding it were not completely cleared up or even apprehended by the author of the ‘Essay.’ ‘Hath a child,’ he says, ‘an idea of impossibility and identity, before it has of white or black, sweet or sour? Or is it from the knowledge of this principle that it concludes that wormwood rubbed on the nipple hath not the same taste that it used to receive from thence? Is it the actual knowledge of _Impossibile est idem esse et non esse_ that makes a child distinguish between its mother and a stranger, or that makes it fond of the one, and fly the other? Or does the mind regulate itself and its assent by ideas that it never had? Or the understanding draw conclusions from principles which it never yet knew or understood? The names _impossibility_ and _identity_ stand for two ideas, so far from being innate, or born with us, that I think it requires great care and attention to form them right in our understandings. They are so far from being brought into the world with us, so remote from the thoughts of infancy and childhood, that I believe upon examination it will be found that many grown men want them.