Summa summae S. Thomae, Tomus II

I say 1°: The creature is the ultimate end of one sinning mortally¹, according to that word of the Apostle, Philip., I, 19, of the gluttonous: Whose God is their belly.

It is proved 1° from Aug., who in many places places the whole perversity of human life in this, that he enjoys things to be used and uses things to be enjoyed²; but to enjoy, according to the same Aug., lib. XI de Civit., c. 25, and elsewhere, is to adhere to something as to an ultimate end. But he who sins mortally enjoys things to be used; for he does not use them on account of God, since on their account he forsakes God. Therefore.

It is proved 2º by reason. What man perversely loves by sinning mortally, he does not love as a means, or as an intermediate end subordinated to God, otherwise he would not sin; and moreover it is clear because, according to Scripture, Isa., I, 2, by sinning mortally he spurns³ God, and I Reg., XII, 10, forsakes⁴ God. Therefore he loves it as an ultimate end, or as a mean or intermediate end subordinated to another creature, and that other creature will be for him the ultimate end.

But there remains the question: what creature is the ultimate end of one sinning mortally. Concerning which

I say 2º: The ultimate end of one sinning mortally is his own and private good, not in itself, but inordinately loved even to contempt of God and exclusion of grace and charity.

The first part is proved. That is the ultimate end of one sinning mortally which he loves for its own sake, and under whose reason he loves other things. But one sinning mortally loves his own and private good for its own sake, and the other particular goods which he pursues he loves by reason of his own and private good. Therefore. — The major is the definition of the ultimate end. — Proof of the minor. In every mortal sin the sinner loves a changeable good, because in it he finds, or apprehends, or imagines some convenience and advantage for himself. For either he apprehends this good as serving him, and thus apprehends it as good for himself; or he apprehends that he ought to serve that good, as idolaters worshipped idols for gods, and thus he apprehends its serving him as convenient and advantageous, just as a friend apprehends serving his friend as convenient and good for himself. Therefore whatever particular goods one sinning mortally pursues, those he loves under the reason of his own and private good.

The second part is proved. The ultimate end of one sinning mortally is opposed to God and irreferable to him. But one's own and private good in itself is not opposed to God and irreferable to him, but only cuts itself off from him; but as inordinately loved even to contempt of God and exclusion of grace, it is opposed to God and irreferable to him. Therefore.

From this you will infer that not everything the sinner does is mortal sin; nay rather, sometimes it is morally good, as honoring parents, paying debts⁵, etc. For although these are not actually and explicitly referred to God in the sinner, they are nevertheless not irreferable of themselves; nay they are referred virtually and implicitly, as I shall say elsewhere. Hence also you have the solution of objections that can be made.

I say 3º: The ultimate end of one sinning venially, whether sinner or just man, is beatitude as such, or to be well and happy. For thus the ultimate end is had positively, and it is easily conceived how it does not exclude charity; because this most common end, since it is necessarily loved and indifferent of itself so as to be applied to a good or evil object, gives no honesty or malice to the act of itself, but abstracts from both. Consult dissert. I de Ultimo fine, a. 4 and 5.

Hence you will understand in what sense St. Thomas says in many places that venial sin is habitually referred to God. For the holy Doctor means nothing else than that venial sin in the just man is compatible with charity, and does not exclude it; because habitual relation, as I said in dissert. I de Ultimo fine, a. 5, signifies pure concomitance of some habit with an act, without any influx, whether actual or virtual. Whence, just as if a just man while sleeping were reciting prayers, he would be said to refer them habitually to God, on account of the concomitance of the habit of charity; so, while he sins venially, his sin is said to be referred habitually to God, on account of the charity concomitant, which he does not expel.