Jacques Maritain on the Soul and ImmortalityThe Range of Reason (London: Geoffrey Bles Ltd. And New York: Charles Scribner's Sons, 1953), 60.
A spiritual soul cannot be corrupted, since it possesses no matter; it cannot be disintegrated, since it has no substantial parts; it cannot lose its individual unity, since it is self-subsisting, nor its internal energy, since it contains within itself all the sources of its energies. The human soul cannot die. Once it exists, it cannot disappear; it will necessarily exist forever, endure without end. Thus philosophic reason is able to prove the immortality of the human soul in a demonstrative manner.