....[According to Kant] infinite progress is possible only if the existence and personality of rational beings continue on into infinity; the immortality of the soul is therefore a postulate of pure practical reason. The attainment of the highest good, the coincidence of happiness and virtue, lies in the far reaches of infinite personal existence and is not possible in a finite existence. Kant was so completely imbued with the truth of this train of thought that he was astonished that philosophers could even entertain the possibility of this-worldly perfection and fulfillment [Sinnerfüllung] of existence.
"When we see ourselves compelled to seek at such distance—namely in the connection with an intelligible world—the possibility of the highest good, which reason presents to all rational creatures as the goal of all their moral wishes, it must appear strange that philosophers of both ancient and modern times have been able to find happiness with virtue in very proper proportion even in this life (in the world of the senses) or, at any rate, have been able to persuade themselves that they had."1
Based on his assumed contradiction between sensory existence and reason in earthly life, Kant considered the finitist observation on personality pointless. The essence of man, Kant maintained, consists of his intelligible rational personality, and as long as this is bound to man's nature, it cannot exclusively influence his volition [Willkür]; the tendency to follow one's drives [Trieb] can never be completely excluded. Only God's will is holy and as such not capable of any maxims that contradict the moral law.
"For rational but finite beings, only unending progress from lower to higher levels of moral perfection is possible. The Infinite Being, for whom time is nothing, sees in this progress, which for us is endless, a whole appropriate to the moral law; and holiness, which his law inexorably demands in order to be fitting for his justice in the share of the highest good he assigns to each, can be found in a single intellectual intuition of the existence of rational beings."2
Thus the problem of the finiteness of existence is changed because the sensory nature of man's earthly being is seen as only a symptom of finiteness, not its constituent, for the person does not lose any of his finiteness when he dies and lays aside his sensory body. Life in the hereafter is not perfect all at once just because it is freed of its earthly fetters; rather, it is also a finite existence in contrast to the one infinite existence of God.
The complication of the problem through the question of man's sensory nature is resolved, and the essence of his finiteness is placed in the development of the person through an infinite becoming; what for divine intuition is a unified, self-contained substance, resting in its perfection, can only be understood by finite human beings in the infinite process. The incomprehensible disintegration of being in time, which becomes complete and whole again in God's eternity, is for Kant—as it was for Augustine—the formula in which he expresses the nature of finiteness.
From the necessary parallels of temporal disintegration and divine eternity follows his astonishment at attempts to get a finite view of the whole of the person.1.Kant, Kritik der praktischen Vernunft, 115. All quotations are taken from the edition of the Philosophische Bibliothek, Meiner; page numbers are from the Akademie edition. 2. Ibid., 123.