Objection 1. It would seem impossible for the damned, by right and deliberate reason, to wish not to be. For Augustine says (De Lib. Arb. iii, 7): "Consider how great a good it is to be; since both the happy and the unhappy will it; for to be and yet to be unhappy is a greater thing than not to be at all."
Objection 2. Further, Augustine argues thus (De Lib. Arb. iii, 8): "Preference supposes election." But "not to be" is not eligible; since it has not the appearance of good, for it is nothing. Therefore not to be cannot be more desirable to the damned than "to be."
Objection 3. Further, the greater evil is the more to be shunned. Now "not to be" is the greatest evil, since it removes good altogether, so as to leave nothing. Therefore "not to be" is more to be shunned than to be unhappy: and thus the same conclusion follows as above.
On the contrary, It is written (Apocalypse 9:6): "In those days men... shall desire to die, and death shall fly from them."
Further, the unhappiness of the damned surpasses all unhappiness of this world. Now in order to escape the unhappiness of this world, it is desirable to some to die, wherefore it is written (Sirach 41:3-4): "O death, thy sentence is welcome to the man that is in need and to him whose strength faileth; who is in a decrepit age, and that is in care about all things, and to the distrustful that loseth wisdom [Vulgate: 'patience']." Much more, therefore, is "not to be" desirable to the damned according to their deliberate reason.
I answer that, Not to be may be considered in two ways. First, in itself, and thus it can nowise be desirable, since it has no aspect of good, but is pure privation of good. Secondly, it may be considered as a relief from a painful life or from some unhappiness: and thus "not to be" takes on the aspect of good, since "to lack an evil is a kind of good" as the Philosopher says (Ethic. v, 1). In this way it is better for the damned not to be than to be unhappy. Hence it is said (Matthew 26:24): "It were better for him, if that man had not been born," and (Jeremiah 20:14): "Cursed be the day wherein I was born," where a gloss of Jerome observes: "It is better not to be than to be evilly." In this sense the damned can prefer "not to be" according to their deliberate reason [Cf. I, 5, 2, ad 3].
Reply to Objection 1. The saying of Augustine is to be understood in the sense that "not to be" is eligible, not in itself but accidentally, as putting an end to unhappiness. For when it is stated that "to be" and "to live" are desired by all naturally, we are not to take this as referable to an evil and corrupt life, and a life of unhappiness, as the Philosopher says (Ethic. ix, 4), but absolutely.
Reply to Objection 2. Non-existence is eligible, not in itself, but only accidentally, as stated already.
Reply to Objection 3. Although "not to be" is very evil, in so far as it removes being, it is very good, in so far as it removes unhappiness, which is the greatest of evils, and thus it is preferred "not to be."
Source: Summa Theologica (New Advent)