Ante-Nicene Fathers, Vol III:
Tertullian: Part II: Though the Son or Word of God Emanates from the Father, He is Not, Like the Emanations of Valentinus, Separable from the Father. Nor is the Holy Ghost Separable from Either. Illustrations from Nature.

Chapter VIII.—Though the Son or Word of God Emanates from the Father, He is Not, Like the Emanations of Valentinus, Separable from the Father.  Nor is the Holy Ghost Separable from Either. Illustrations from Nature.

If any man from this shall think that I am introducing some προβολή—that is to say, some prolation 7846 of one thing out of another, as Valentinus does when he sets forth Æon from Æon, one after another—then this is my first reply to you: Truth must not therefore refrain from the use of such a term, and its reality and meaning, because heresy also employs it. The fact is, heresy has rather taken it from Truth, in order to mould it into its own counp. 603 terfeit. Was the Word of God put forth or not? Here take your stand with me, and flinch not. If He was put forth, then acknowledge that the true doctrine has a prolation; 7847 and never mind heresy, when in any point it mimics the truth. The question now is, in what sense each side uses a given thing and the word which expresses it. Valentinus divides and separates his prolations from their Author, and places them at so great a distance from Him, that the Æon does not know the Father:  he longs, indeed, to know Him, but cannot; nay, he is almost swallowed up and dissolved into the rest of matter. 7848 With us, however, the Son alone knows the Father, 7849 and has Himself unfolded “the Father’s bosom.” 7850 He has also heard and seen all things with the Father; and what He has been commanded by the Father, that also does He speak. 7851 And it is not His own will, but the Father’s, which He has accomplished, 7852 which He had known most intimately, even from the beginning. “For what man knoweth the things which be in God, but the Spirit which is in Him?” 7853 But the Word was formed by the Spirit, and (if I may so express myself) the Spirit is the body of the Word. The Word, therefore, is both always in the Father, as He says, “I am in the Father;” 7854 and is always with God, according to what is written, “And the Word was with God;” 7855 and never separate from the Father, or other than the Father, since “I and the Father are one.” 7856 This will be the prolation, taught by the truth, 7857 the guardian of the Unity, wherein we declare that the Son is a prolation from the Father, without being separated from Him.  For God sent forth the Word, as the Paraclete also declares, just as the root puts forth the tree, and the fountain the river, and the sun the ray. 7858 For these are προβολαί, or emanations, of the substances from which they proceed. I should not hesitate, indeed, to call the tree the son or offspring of the root, and the river of the fountain, and the ray of the sun; because every original source is a parent, and everything which issues from the origin is an offspring.  Much more is (this true of) the Word of God, who has actually received as His own peculiar designation the name of Son. But still the tree is not severed from the root, nor the river from the fountain, nor the ray from the sun; nor, indeed, is the Word separated from God.  Following, therefore, the form of these analogies, I confess that I call God and His Word—the Father and His Son—two. For the root and the tree are distinctly two things, but correlatively joined; the fountain and the river are also two forms, but indivisible; so likewise the sun and the ray are two forms, but coherent ones. Everything which proceeds from something else must needs be second to that from which it proceeds, without being on that account separated.  Where, however, there is a second, there must be two; and where there is a third, there must be three. Now the Spirit indeed is third from God and the Son; just as the fruit of the tree is third from the root, or as the stream out of the river is third from the fountain, or as the apex of the ray is third from the sun. Nothing, however, is alien from that original source whence it derives its own properties.  In like manner the Trinity, flowing down from the Father through intertwined and connected steps, does not at all disturb the Monarchy, 7859 whilst it at the same time guards the state of the Economy. 7860

Footnotes

“The word προβολή properly means anything which proceeds or is sent forth from the substance of another, as the fruit of a tree or the rays of the sun. In Latin, it is translated by prolatio, emissio, or editio, or what we now express by the word development. In Tertullian’s time, Valentinus had given the term a material signification.  Tertullian, therefore, has to apologize for using it, when writing against Praxeas, the forerunner of the Sabellians” (Newman’s Arians, ii. 4; reprint, p. 101).

προβολή.

See Adv. Valentin. cc. xiv. xv.

Matt. xi. 27.

John i. 18.

John viii. 26.

John vi. 38.

1 Cor. ii. 11.

John xiv. 11.

John i. 1.

John x. 30.

Literally, the προβολή, “of the truth.”

[Compare cap. iv. supra.]

Or oneness of the divine empire.

Or dispensation of the divine tripersonality. See above ch. ii.