Objection 1. It would seem that the act of knowledge here acquired does not remain in the separated soul. For the Philosopher says (De Anima i, 4), that when the body is corrupted, "the soul neither remembers nor loves." But to consider what is previously known is an act of memory. Therefore the separated soul cannot retain an act of knowledge here acquired.
Objection 2. Further, intelligible species cannot have greater power in the separated soul than they have in the soul united to the body. But in this life we cannot understand by intelligible species without turning to phantasms, as shown above (Question 84, Article 7). Therefore the separated soul cannot do so, and thus it cannot understand at all by intelligible species acquired in this life.
Objection 3. Further, the Philosopher says (Ethic. ii, 1), that "habits produce acts similar to those whereby they are acquired." But the habit of knowledge is acquired here by acts of the intellect turning to phantasms: therefore it cannot produce any other acts. These acts, however, are not adapted to the separated soul. Therefore the soul in the state of separation cannot produce any act of knowledge acquired in this life.
On the contrary, It was said to Dives in hell (Luke 16:25): "Remember thou didst receive good things in thy lifetime."
I answer that, Action offers two things for our consideration--its species and its mode. Its species comes from the object, whereto the faculty of knowledge is directed by the (intelligible) species, which is the object's similitude; whereas the mode is gathered from the power of the agent. Thus that a person see a stone is due to the species of the stone in his eye; but that he see it clearly, is due to the eye's visual power. Therefore as the intelligible species remain in the separated soul, as stated above (Article 5), and since the state of the separated soul is not the same as it is in this life, it follows that through the intelligible species acquired in this life the soul apart from the body can understand what it understood formerly, but in a different way; not by turning to phantasms, but by a mode suited to a soul existing apart from the body. Thus the act of knowledge here acquired remains in the separated soul, but in a different way.
Reply to Objection 1. The Philosopher speaks of remembrance, according as memory belongs to the sensitive part, but not as belonging in a way to the intellect, as explained above (Question 79, Article 6).
Reply to Objection 2. The different mode of intelligence is produced by the different state of the intelligent soul; not by diversity of species.
Reply to Objection 3. The acts which produce a habit are like the acts caused by that habit, in species, but not in mode. For example, to do just things, but not justly, that is, pleasurably, causes the habit of political justice, whereby we act pleasurably. (Cf. Aristotle, Ethic. v, 8: Magn. Moral. i, 34).
Source: Summa Theologica (New Advent)