Thomas Aquinas, Compendium of Theology

We go on to consider the nature of the activity exercised by risen men. Each living being must have some activity that mainly engrosses its attention, and its life is said to consist in this occupation. Thus those who cultivate pleasure more than anything else, are said to lead a voluptuous life; those who give their time to contemplation, are said to lead a contemplative life; and those who devote their energies to civil government, are said to lead a political life. We have shown that risen men will have no occasion to use food or the reproductive functions, although all bodily activity seems to tend in the direction of such use. But, even if the exercise of bodily functions ceases, there remain spiritual activities, in which man's ultimate end consists, as we have said; and the risen are in a position to achieve this end once they are freed from their former condition of corruption and changeableness. Of course, man's last end consists, not in spiritual acts of any sort whatever, but in the vision of God according to His essence, as was stated above. And God is eternal; hence the intellect must be in contact with eternity. Accordingly, just as those who give their time to pleasure are said to lead a voluptuous life, so those who enjoy the vision of God possess eternal life, as is indicated in John 17:3: "This is eternal life: that they may know Thee, the only true God, and Jesus Christ whom Thou hast sent."