formed from πάσχω, beyond, and ἐνεργεία, I animate or enliven, in the ancient philosophy, signified the passage or transmigration of the soul of a man after death into the body of some other animal. Pythagoras and his followers held, that after death men's souls passed into other bodies of different kinds, according to the manner of life which they had led. If they had been vicious, they were imprisoned in the bodies of miserable beasts, there to do penance for several ages, at the expiration of which they returned again to animate human forms. But if they lived virtuously, the body of some happier brute, or even of a human creature, was destined to be their new habitation. What led Pythagoras into this opinion was, the persuasion which he had that the soul was not of a perishable nature, and from which he concluded that it must remove into some other body upon its abandoning its actual habitation. Lucan treats this doctrine as a kind of officious lie, contrived to mitigate the apprehension of death, by persuading men that they had changed their lodging, and only ceased to live in order to begin a new life. Reuchlin denies this doctrine, and maintains that the metempsychosis of Pythagoras implied nothing more than a similitude of manners, desires, and studies, which formerly existed in some person deceased, and were subsequently revived in another. Thus, when it was said that Euphorbus was revived in Pythagoras, no more was meant than that the martial virtue which had shone in Euphorbus at the time of the Trojan war, was now in some measure revived in Pythagoras, by reason of the great respect he bore to the athlete. For those people, wondering how a philosopher should be so much taken with men of the sword, he palliated the matter by saying that the soul of Euphorbus, meaning thereby his genius, disposition, and inclinations, were revived in him; and this gave occasion to the report that the soul of Euphorbus, who perished in the Trojan war, had transmigrated into Pythagoras. Ficinus asserts that what Plato said of the migration of a human soul into a brute, is allegorically said, and to be understood, only of those manners, affections, and habits which have degenerated into a beastly nature by vice. Serranus, though he allows some force to this interpretation, yet rather inclines to understand the metempsychosis as meaning a resurrection. Pythagoras is said to have borrowed the notion of a metempsychosis from the Egyptians; but others maintain that he received it from the ancient Brahmins. It is still retained amongst the Banians and other idolaters of India and China, and forms the principal foundation of their religion; indeed, so bigoted are they to this tenet, that they not only forbear eating any thing which has life, but many of them even refuse to defend themselves against wild beasts. They burn no wood, lest some little animacule should be consumed in it; and are so very charitable, that they will redeem from the hands of strangers any animals which they find ready to be killed.

(from μετα, post, and επιστρα, cado, I fall), a term in chronology, expressing the solar equation necessary to prevent the new moon from happening a day too late. Metempsysis is contradistinguished from preempsysis, which signifies the lunar equation necessary to prevent the new moon from happening a day too soon. As the new moons run a little backwards, that is, come a day too soon at the end of 312 years and a half, by the preempsysis a day is added every 300 years, and another every 2400 years. On the other hand, by the metempsysis, a bissextile day is suppressed each 134 years, that is, three times in 400 years. These alterations are never made but at the end of each century, that period being very remarkable, and rendering the practice of the calendar easy. There are three rules for making this addition or suppression of the bissextile day, and, consequently, for changing the index of the epacts. First, when there is a metempsysis without a preempsysis, the next following or lower index must be taken. Secondly, when there is a preempsysis without a metempsysis, the next preceding or superior index is to be taken. Thirdly, when there are both a metempsysis and a preempsysis, or when there is neither the one nor the other, the same index is preserved. Thus, in 1600, we had D; in 1700, by reason of the metempsysis, C was taken; in 1800, there was both a preempsysis and a metempsysis, therefore the same index was retained. In 1900 there will be a metempsysis again, when B will be taken; and this will be preserved in 2000, because there will then be neither the one nor the other. This is as far as we need compute for it. But Clavius has calculated a cycle of 301,800 years, at the end of which period the same indices will return in the same order.