Objection 1. It would seem that the contemplative life is not continuous. For the contemplative life consists essentially in things pertaining to the intellect. Now all the intellectual perfections of this life will be made void, according to (1 Corinthians 13:8), "Whether prophecies shall be made void, or tongues shall cease, or knowledge shall be destroyed." Therefore the contemplative life is made void.
Objection 2. Further, a man tastes the sweetness of contemplation by snatches and for a short time only: wherefore Augustine says (Confess. x, 40), "Thou admittest me to a most unwonted affection in my inmost soul, to a strange sweetness... yet through my grievous weight I sink down again." Again, Gregory commenting on the words of Job 4:15, "When a spirit passed before me," says (Moral. v, 33): "The mind does not remain long at rest in the sweetness of inward contemplation, for it is recalled to itself and beaten back by the very immensity of the light." Therefore the contemplative life is not continuous.
Objection 3. Further, that which is not connatural to man cannot be continuous. Now the contemplative life, according to the Philosopher (Ethic. x, 7), "is better than the life which is according to man." Therefore seemingly the contemplative life is not continuous.
On the contrary, our Lord said (Luke 10:42): "Mary hath chosen the best part, which shall not be taken away from her," since as Gregory says (Hom. xiv in Ezech.), "the contemplative life begins here so that it may be perfected in our heavenly home."
I answer that, A thing may be described as continuous in two ways: first, in regard to its nature; secondly, in regard to us. It is evident that in regard to itself contemplative life is continuous for two reasons: first, because it is about incorruptible and unchangeable things; secondly, because it has no contrary, for there is nothing contrary to the pleasure of contemplation, as stated in Topic. i, 13. But even in our regard contemplative life is continuous--both because it is competent to us in respect of the incorruptible part of the soul, namely the intellect, wherefore it can endure after this life--and because in the works of the contemplative life we work not with our bodies, so that we are the more able to persevere in the works thereof, as the Philosopher observes (Ethic. x, 7).
Reply to Objection 1. The manner of contemplation is not the same here as in heaven: yet the contemplative life is said to remain by reason of charity, wherein it has both its beginning and its end. Gregory speaks in this sense (Hom. xiv in Ezech.): "The contemplative life begins here, so as to be perfected in our heavenly home, because the fire of love which begins to burn here is aflame with a yet greater love when we see Him Whom we love."
Reply to Objection 2. No action can last long at its highest pitch. Now the highest point of contemplation is to reach the uniformity of Divine contemplation, according to Dionysius [Cf. Coel. Hier. iii], and as we have stated above (6, ad 2). Hence although contemplation cannot last long in this respect, it can be of long duration as regards the other contemplative acts.
Reply to Objection 3. The Philosopher declares the contemplative life to be above man, because it befits us "so far as there is in us something divine" (Ethic. x, 7), namely the intellect, which is incorruptible and impassible in itself, wherefore its act can endure longer.
Source: Summa Theologica (New Advent)