The Son and Spirit belong to the Father and so are not the same as the Father, but are both God

For both the Spirit is the substance of the Word, and the Word is the operation of the Spirit, and the Two are One (and the same). Now John must mean One when he speaks of Him as “having been made flesh,” and the angel Another when he announces Him as “about to be born,” if the Spirit is not the Word, and the Word the Spirit. For just as the Word of God is not actually He whose Word He is, so also the Spirit (although He is called God) is not actually He whose Spirit He is said to be. Nothing which belongs to something else is actually the very same thing as that to which it belongs.

…And thus the Spirit is God, and the Word is God, because proceeding from God, but yet is not actually the very same as He from whom He proceeds. Now that which is God of God, although He is an actually existing thing, yet He cannot be God Himself (exclusively), but so far God as He is of the same substance as God Himself, and as being an actually existing thing

Tertullian
Against Praxeas
Chapter XXVI

Father, Son and Spirit are three persons but one essence

Thus the connection of the Father in the Son, and of the Son in the Paraclete, produces three coherent Persons, who are yet distinct One from Another. These Three are one essence, not one Person, as it is said, “I and my Father are One,” in respect of unity of substance not singularity of number.

Tertullian
Against Praxeas
Chapter XXV

John 1:1 can only be interpreted to mean one thing — Christ is God but distinct from the Father

…first of all there comes at once to hand the preamble of John to his Gospel, which shows us what He previously was who had to become flesh.  “In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God: all things were made by Him, and without Him was nothing made.” Now, since these words may not be taken otherwise than as they are written, there is without doubt shown to be One who was from the beginning, and also One with whom He always was: one the Word of God, the other God (although the Word is also God, but God regarded as the Son of God, not as the Father); One through whom were all things, Another by whom were all things.  But in what sense we call Him Another we have already often described. In that we called Him Another, we must needs imply that He is not identical—not identical indeed, yet not as if separate; Other by dispensation, not by division.

Tertullian
Against Praxeas
Chapter XXI

Praxeas’ heresy mistakenly uses a few passages against a great many

For, inasmuch as only a few testimonies are to be found (making for them) in the general mass, they pertinaciously set off the few against the many, and assume the later against the earlier. The rule, however, which has been from the beginning established for every case, gives its prescription against the later assumptions, as indeed it also does against the fewer.

Tertullian
Against Praxeas
Chapter XX

The persons of the Godhead do not make multiple gods

Therefore, if they have determined that the Father and the Son must be regarded as one and the same, for the express purpose of vindicating the unity of God, that unity of His is preserved intact; for He is one, and yet He has a Son, who is equally with Himself comprehended in the same Scriptures. Since they are unwilling to allow that the Son is a distinct Person, second from the Father, lest, being thus second, He should cause two Gods to be spoken of, we have shown above that Two are actually described in Scripture as God and Lord. And to prevent their being offended at this fact, we give a reason why they are not said to be two Gods and two Lords, but that they are two as Father and Son; and this not by severance of their substance, but from the dispensation wherein we declare the Son to be undivided and inseparable from the Father,—distinct in degree, not in state. And although, when named apart, He is called God, He does not thereby constitute two Gods, but one; and that from the very circumstance that He is entitled to be called God, from His union with the Father.

Tertullian
Against Praxeas
Chapter XIX

It is still correct to say that the Word created alone

Inasmuch, then, as the heaven was prepared when Wisdom was present in the Word, and since all things were made by the Word, it is quite correct to say that even the Son stretched out the heaven alone, because He alone ministered to the Father’s work. It must also be He who says, “I am the First, and to all futurity I AM.” The Word, no doubt, was before all things.

Tertullian
Against Praxeas
Chapter XIX

The Son shares the titles of the Father also

“All things,” says He, “which the Father hath are mine.” Then why not His names also? When, therefore, you read of Almighty God, and the Most High, and the God of hosts, and the King of Israel, the “One that is,” consider whether the Son also be not indicated by these designations, who in His own right is God Almighty, in that He is the Word of Almighty God, and has received power over all; is the Most High, in that He is “exalted at the right hand of God,” as Peter declares in the Acts; is the Lord of hosts, because all things are by the Father made subject to Him; is the King of Israel because to Him has especially been committed the destiny of that nation; and is likewise “the One that is,” because there are many who are called Sons, but are not.

As if, indeed, He which is to come were not almighty; whereas even the Son of the Almighty is as much almighty as the Son of God is God.

Tertullian
Against Praxeas
Chapter XVII

The Logos interacted with the world in the Old Testament as the agent of the Father

It is the Son, therefore, who has been from the beginning administering judgment, throwing down the haughty tower, and dividing the tongues, punishing the whole world by the violence of waters, raining upon Sodom and Gomorrah fire and brimstone, as the Lord from the Lord.

…Thus was He ever learning even as God to converse with men upon earth, being no other than the Word which was to be made flesh.

…and therefore that it was uniformly one God, even the Father, who at all times did Himself the things which were really done by Him through the agency of the Son.

Tertullian
Against Praxeas
Chapter XVI

Paul beheld Christ and knew He was God

Him, too, did Paul behold; but yet he saw not the Father. “Have I not,” he says, “seen Jesus Christ our Lord?” Moreover, he expressly called Christ God, saying: “Of whom are the fathers, and of whom as concerning the flesh Christ came, who is over all, God blessed for ever.”

Tertullian
Against Praxeas
Chapter XV

The Word is God of God

Now the Word of life became flesh, and was heard, and was seen, and was handled, because He was flesh who, before He came in the flesh, was the “Word in the beginning with God” the Father, and not the Father with the Word. For although the Word was God, yet was He with God, because He is God of God; and being joined to the Father, is with the Father.

Tertullian
Against Praxeas
Chapter XV