Here, then, we have a conception of the origin and nature of the human soul as a spiritual existence, quite as distinctly presented as it can be by human reason. Stripped of the machinery by which Plato supposes the soul to have come into existence, his conception of its origin and nature is the most remarkable contribution which philosophy, apart from the aid of what is called inspiration, has made to our means of speculating upon this great theme. Of course, it affords, with all the machinery of which Plato makes use, no explanation of the point or the time of junction between the soul and the body. But, as a conception of what in the poverty of language must be called the substance of the soul, of its spiritual and immortal nature, of its distinctive existence separate from what we know as matter, whether Plato borrowed more or less from other philosophers who preceded him, it is a very distinct presentation of the nature of the human mind. Turn now to what can be extracted from the Darwinian theory of the origin and nature of the human mind, and observe where it holds with and where it breaks from the parallelism between it and the Platonic theory. The doctrine of evolution, so called, presents to us no distinct suggestion that the mind of man is a separate and special creation. Rejecting, and very properly rejecting, the Platonic idea of an existence of the human soul anterior to the birth of the individual, the Darwinian theory supposes that in the long course of time, during which natural and sexual selection were operating to produce higher and still higher animals, there came about, in the earlier and primitive organizations, a habit of the animal to act in a certain way; that this habit descended to offspring; that it became developed into what is now called instinct; and that instinct became developed into what we now call mind. I know not how otherwise to interpret Mr. Darwin's repeated affirmations that, in comparing the mental powers of man and those of the lower animals, there can be detected no difference in kind, but that the difference is one of degree only; that there is no fundamental difference, or difference in nature, between the mental powers of an ape and a man, or between the mental power of one of the lowest fishes, as a lamprey or lancelet, and that of one of the higher apes; that both of these intervals, that between the ape and man, and that between the lancelet and the ape, which are much wider in the latter case than in the former, are filled up by numberless gradations.[33] If this be true, it must be because the lancelet, supposing that animal to be the progenitor, formed a habit of acting by an implanted impulse, which became, under the operation of natural and sexual selection, confirmed, developed, and increased in its descendants, until it not only amounted to what is called instinct, but took on more complex habits until something akin to reason was developed. As the higher