Ante-Nicene Fathers, Vol III:
Tertullian: Part I: The Soul's Parts.  Elements of the Rational Soul.

Chapter XVI.—The Soul’s Parts. Elements of the Rational Soul.

That position of Plato’s is also quite in keeping with the faith, in which he divides the soul into two parts—the rational and the irrational.  To this definition we take no exception, except that we would not ascribe this twofold distinction to the nature (of the soul). It is the rational element which we must believe to be its natural condition, impressed upon it from its very first creation by its Author, who is Himself essentially rational. For how should that be other than rational, which God produced on His own prompting; nay more, which He expressly sent forth by His own afflatus or breath? The irrational element, however, we must understand to have accrued later, as having proceeded from the instigation of the serpent—the very achievement of (the first) transgression—which thenceforward became inherent in the soul, and grew with its growth, assuming the manner by this time of a natural development, happening as it did immediately at the beginning of nature.  But, inasmuch as the same Plato speaks of the rational element only as existing in the soul of God Himself, if we were to ascribe the irrational element likewise to the nature which our soul has received from God, then the irrational element will be equally derived from God, as being a natural production, because God is the author of nature. Now from the devil proceeds the incentive to sin. All sin, however, is irrational: therefore the irrational proceeds from the devil, from whom sin proceeds; and it is exp. 195 traneous to God, to whom also the irrational is an alien principle.  The diversity, then, between these two elements arises from the difference of their authors. When, therefore, Plato reserves the rational element (of the soul) to God alone, and subdivides it into two departments: the irascible, which they call θυμικόν, and the concupiscible, which they designate by the term ἐπιθυμητικόν (in such a way as to make the first common to us and lions, and the second shared between ourselves and flies, whilst the rational element is confined to us and God)—I see that this point will have to be treated by us, owing to the facts which we find operating also in Christ. For you may behold this triad of qualities in the Lord. There was the rational element, by which He taught, by which He discoursed, by which He prepared the way of salvation; there was moreover indignation in Him, by which He inveighed against the scribes and the Pharisees; and there was the principle of desire, by which He so earnestly desired to eat the passover with His disciples. 1599 In our own cases, accordingly, the irascible and the concupiscible elements of our soul must not invariably be put to the account of the irrational (nature), since we are sure that in our Lord these elements operated in entire accordance with reason. God will be angry, with perfect reason, with all who deserve His wrath; and with reason, too, will God desire whatever objects and claims are worthy of Himself.  For He will show indignation against the evil man, and for the good man will He desire salvation. To ourselves even does the apostle allow the concupiscible quality. “If any man,” says he, “desireth the office of a bishop, he desireth a good work.” 1600 Now, by saying “a good work,” he shows us that the desire is a reasonable one. He permits us likewise to feel indignation.  How should he not, when he himself experiences the same? “I would,” says he, “that they were even cut off which trouble you.” 1601 In perfect agreement with reason was that indignation which resulted from his desire to maintain discipline and order. When, however, he says, “We were formerly the children of wrath,” 1602 he censures an irrational irascibility, such as proceeds not from that nature which is the production of God, but from that which the devil brought in, who is himself styled the lord or “master” of his own class, “Ye cannot serve two masters,” 1603 and has the actual designation of “father:”  “Ye are of your father the devil.” 1604 So that you need not be afraid to ascribe to him the mastery and dominion over that second, later, and deteriorated nature (of which we have been speaking), when you read of him as “the sewer of tares,” and the nocturnal spoiler of the crop of corn. 1605

Footnotes

Luke xxii. 15.

1 Tim. iii. 1.

Gal. v. 12.

Eph. ii. 3.

Matt. vi. 24.

John vi. 44.

Matt. xiii. 25.