Ante-Nicene Fathers, Vol III:
Tertullian: Part II: Christ's Human Nature.  The Flesh and the Soul Both Fully and Unconfusedly Contained in It.

p. 533 Chapter XIII.—Christ’s Human Nature.  The Flesh and the Soul Both Fully and Unconfusedly Contained in It.

The soul became flesh that the soul might become visible. 7123 Well, then, did the flesh likewise become soul that the flesh might be manifested? 7124 If the soul is flesh, it is no longer soul, but flesh. If the flesh is soul, it is no longer flesh, but soul. Where, then, there is flesh, and where there is soul, it has become both one and the other. 7125 Now, if they are neither in particular, although they become both one and the other, it is, to say the least, very absurd, that we should understand the soul when we name the flesh, and when we indicate the soul, explain ourselves as meaning the flesh. All things will be in danger of being taken in a sense different from their own proper sense, and, whilst taken in that different sense, of losing their proper one, if they are called by a name which differs from their natural designation.  Fidelity in names secures the safe appreciation of properties. When these properties undergo a change, they are considered to possess such qualities as their names indicate. Baked clay, for instance, receives the name of brick. 7126 It retains not the name which designated its former state, 7127 because it has no longer a share in that state.  Therefore, also, the soul of Christ having become flesh, 7128 cannot be anything else than that which it has become nor can it be any longer that which it once was, having become indeed 7129 something else. And since we have just had recourse to an illustration, we will put it to further use. Our pitcher, then, which was formed of the clay, is one body, and has one name indicative, of course, of that one body; nor can the pitcher be also called clay, because what it once was, it is no longer. Now that which is no longer (what it was) is also not an inseparable property. 7130 And the soul is not an inseparable property. Since, therefore, it has become flesh, the soul is a uniform solid body; it is also a wholly incomplex being, 7131 and an indivisible substance. But in Christ we find the soul and the flesh expressed in simple unfigurative 7132 terms; that is to say, the soul is called soul, and the flesh, flesh; nowhere is the soul termed flesh, or the flesh, soul; and yet they ought to have been thus (confusedly) named if such had been their condition. The fact, however, is that even by Christ Himself each substance has been separately mentioned by itself, conformably of course, to the distinction which exists between the properties of both, the soul by itself, and the flesh by itself.  “My soul,” says He, “is exceeding sorrowful, even unto death;” 7133 and “the bread that I will give is my flesh, (which I will give) for the life 7134 of the world.” 7135 Now, if the soul had been flesh, there would have only been in Christ the soul composed of flesh, or else the flesh composed of soul. 7136 Since, however, He keeps the species distinct, the flesh and the soul, He shows them to be two. If two, then they are no longer one; if not one, then the soul is not composed of flesh, nor the flesh of soul. For the soul-flesh, or the flesh-soul, is but one; unless indeed He even had some other soul apart from that which was flesh, and bare about another flesh besides that which was soul. But since He had but one flesh and one soul,—that “soul which was sorrowful, even unto death,” and that flesh which was the “bread given for the life of the world,”—the number is unimpaired 7137 of two substances distinct in kind, thus excluding the unique species of the flesh-comprised soul.

Footnotes

Ostenderetur: or, “that it might prove itself soul.”

Or, “that it might show itself flesh.”

Alterutrum: “no matter which.”

Testæ: a pitcher, perhaps.

Generis.

Tertullian quotes his opponent’s opinion here.

Silicet: in reference to the alleged doctrine.

Non adhæret.

Singularitas tota.

Nudis.

Matt. xxvi. 38. Tertullian’s quotation is put interrogatively.

“The salvation” (salute) is Tertullian’s word.

John vi. 51.

Above, beginning of chap. x.

Salvus.