Plato's views of the immortality of the soul offer a striking contrast to those of the popular philosophy and superstition of his time. They recall, in many respects, the doctrines of India. In Greece, those who held the most enlarged views entertained what might be termed a doctrine of semi-immortality. They looked for a continuance of the soul in an endless futurity, but gave themselves no concern about the eternity which is past. But Plato considered the soul as having already eternally existed, the present life being only a moment in our career; he looked forward with an undoubting faith to the changes through which we must hereafter pass. As sparks issue forth from a flame, so doubtless to his imagination did the soul of man issue forth from the soul of the world. Innate ideas and the sentiment of pre-existence indicate our past life. By the latter is meant that on some occasion perhaps of trivial concern, or perhaps in some momentous event, it suddenly occurs to us that we have been in like circumstances, and surrounded by the things at that instant present on some other occasion before; but the recollection, though forcibly impressing us with surprise, is misty and confused. With Plato shall we say it was in one of our prior states of existence, and the long-forgotten transactions are now suddenly flashing upon us? [Sidenote: But this arises from the anatomical construction of the brain.] But Plato did not know the double structure and the double action of the brain of man; he did not remember that the mind may lose all recognition of the lapse of time, and, with equal facility, compress into the twinkling of an eye events so numerous that for their occurrence days and even years would seem to be required; or, conversely, that it can take a single, a simple idea, which one would suppose might be disposed of in a moment, and dwell upon it, dilating or swelling it out, until all the hours of a long night are consumed. Of the truth of these singular effects we have not only such testimony as that offered by those who have been restored from death by drowning, who describe the flood of memory rushing upon them in the last moment of their mortal agony, the long train of all the affairs in which they have borne a part seen in an instant, as we see the landscape, with all its various objects, by a flash of lightning at night, and that with appalling distinctness, but also from our own experience in our dreams. It is shown in my Physiology how the phenomena of the sentiment of pre-existence may, upon these principles, be explained, each hemisphere of the brain thinking for itself, and the mind deluded as respects the lapse of time, mistaking these simultaneous actions for successive ones, and referring one of the two impressions to an indistinct and misty past. To Plato such facts as these afforded copious proofs of the prior existence of the soul, and strong foundations for a faith in its future life.