Christ, as God, descended to Hades so that we won’t have to

Now although Christ is God, yet, being also man, “He died according to the Scriptures,” and “according to the same Scriptures was buried.” With the same law of His being He fully complied, by remaining in Hades in the form and condition of a dead man; nor did He ascend into the heights of heaven before descending into the lower parts of the earth, that He might there make the patriarchs and prophets partakers of Himself. (This being the case), you must suppose Hades to be a subterranean region, and keep at arm’s length those who are too proud to believe that the souls of the faithful deserve a place in the lower regions. These persons, who are “servants above their Lord, and disciples above their Master,” would no doubt spurn to receive the comfort of the resurrection, if they must expect it in Abraham’s bosom. But it was for this purpose, say they, that Christ descended into hell, that we might not ourselves have to descend thither.

Tertullian
A Treatise on the Soul
Chapter LV

The soul is cleansed and purified upon death

Undoubtedly, when the soul, by the power of death, is released from its concretion with the flesh, it is by the very release cleansed and purified: it is, moreover, certain that it escapes from the veil of the flesh into open space, to its clear, and pure, and intrinsic light; and then finds itself enjoying its enfranchisement from matter, and by virtue of its liberty it recovers its divinity, as one who awakes out of sleep passes from images to verities. Then it tells out what it sees; then it exults or it fears, according as it finds what lodging is prepared for it, as soon as it sees the very angel’s face, that arraigner of souls, the Mercury of the poets.

Tertullian
A Treatise on the Soul
Chapter LIII

Sleep is an icon of the bodily resurrection

Accordingly, when the body shakes off its slumber, it asserts before your eye the resurrection of the dead by its own resumption of its natural functions.  Such, therefore, must be both the natural reason and the reasonable nature of sleep. If you only regard it as the image of death, you initiate faith, you nourish hope, you learn both how to die and how to live, you learn watchfulness, even while you sleep.

Tertullian
A Treatise on the Soul
Chapter XLIII

Man is not totally depraved because the image of God is not lost

For, as we have said before, the corruption of our nature is another nature having a god and father of its own, namely the author of (that) corruption.  Still there is a portion of good in the soul, of that original, divine, and genuine good, which is its proper nature.  For that which is derived from God is rather obscured than extinguished. It can be obscured, indeed, because it is not God; extinguished, however, it cannot be, because it comes from God. As therefore light, when intercepted by an opaque body, still remains, although it is not apparent, by reason of the interposition of so dense a body; so likewise the good in the soul, being weighed down by the evil, is, owing to the obscuring character thereof, either not seen at all, its light being wholly hidden, or else only a stray beam is there visible where it struggles through by an accidental outlet. Thus some men are very bad, and some very good; but yet the souls of all form but one genus: even in the worst there is something good, and in the best there is something bad. For God alone is without sin; and the only man without sin is Christ, since Christ is also God.

Tertullian
A Treatise on the Soul
Chapter XLI

Men’s souls return to their bodies to be judged

Accordingly, God’s judgment will be more full and complete, because it will be pronounced at the very last, in an eternal irrevocable sentence, both of punishment and of consolation, (on men whose) souls are not to transmigrate into beasts, but are to return into their own proper bodies. And all this once for all, and on “that day, too, of which the Father only knoweth;” (only knoweth,) in order that by her trembling expectation faith may make full trial of her anxious sincerity, keeping her gaze ever fixed on that day, in her perpetual ignorance of it, daily fearing that for which she yet daily hopes.

Tertullian
A Treatise on the Soul
Chapter XXXIII

The soul is created simultaneously with the body

How, then, is a living being conceived? Is the substance of both body and soul formed together at one and the same time? Or does one of them precede the other in natural formation? We indeed maintain that both are conceived, and formed, and perfectly simultaneously, as well as born together; and that not a moment’s interval occurs in their conception, so that, a prior place can be assigned to either.

Tertullian
A Treatise on the Soul
Chapter XXVII

The heretics claim souls are created by angels and preexist the body

Some suppose that they came down from heaven, with as firm a belief as they are apt to entertain, when they indulge in the prospect of an undoubted return thither. Saturninus, the disciple of Menander, who belonged to Simon’s sect, introduced this opinion: he affirmed that man was made by angels.

…Now, to procure belief in all this—that the soul had formerly lived with God in the heavens above, sharing His ideas with Him, and afterwards came down to live with us on earth, and whilst here recollects the eternal patterns of things which it had learnt before—he elaborated his new formula, μαθήσεις ἀναμνήσεις, which means that “learning is reminiscence;” implying that the souls which come to us from thence forget the things amongst which they formerly lived, but that they afterwards recall them, instructed by the objects they see around them. Forasmuch, therefore, as the doctrines which the heretics borrow from Plato are cunningly defended by this kind of argument, I shall sufficiently refute the heretics if I overthrow the argument of Plato.

…Amongst so many nations, in so great a crowd of sages, Plato, to be sure, is the only man who has combined the oblivion and the recollection of ideas. Now, since this main argument of his by no means keeps its ground, it follows that its entire superstructure must fall with it, namely, that souls are supposed to be unborn, and to live in the heavenly regions, and to be instructed in the divine mysteries thereof; moreover, that they descend to this earth, and here recall to memory their previous existence, for the purpose, of course, of supplying to our heretics the fitting materials for their systems.

Tertullian
A Treatise on the Soul
Chapter XXIII and XXIV

The soul is not superior to the body

Our present subject concerns the soul, and the point is to prevent the insidious ascription of a superiority to the intellect or understanding. Now, although the objects which are touched by the intellect are of a higher nature, since they are spiritual, than those which are embraced by the senses, since these are corporeal, it will still be only a superiority in the objects—as of lofty ones contrasted with humble—not in the faculties of the intellect against the senses. For how can the intellect be superior to the senses, when it is these which educate it for the discovery of various truths?

…Two conclusions therefore follow from what we have said: (1) That the intellect is not to be preferred above the senses, on the (supposed) ground that the agent through which a thing exists is inferior to the thing itself; and (2) that the intellect must not be separated from the senses, since the instrument by which a thing’s existence is sustained is associated with the thing itself.

Tertullian
A Treatise on the Soul
Chapter XVIII

God addresses the soul of man to turn it toward him

In short, philosophers themselves, and medical men, even when it is their purpose to discourse about the mind, do in every instance inscribe on their title-page and table of contents, “De Anima” (“A treatise on the soul”).  And that you may also have God’s voucher on the subject, it is the soul which He addresses; it is the soul which He exhorts and counsels, to turn the mind and intellect to Him. It is the soul which Christ came to save; it is the soul which He threatens to destroy in hell; it is the soul (or life) which He forbids being made too much of; it is His soul, too (or life), which the good Shepherd Himself lays down for His sheep. It is to the soul, therefore, that you ascribe the supremacy; in it also you possess that union of substance, of which you perceive the mind to be the instrument, not the ruling power.

Tertullian
A Treatise on the Soul
Chapter XIII