Now, leaving on one side the question as to whether it is good theology--and I do not say good reasoning because all this lies outside the sphere of reason--to confound the substance of the body--the body, not the soul--of Christ with the very substance of Divinity--that is to say, with God Himself--it would appear impossible that one so ardently desirous of the immortality of the soul as William James, a man whose whole philosophy aims simply at establishing this belief on rational grounds, should not have perceived that the pragmatic application of the concept of substance to the doctrine of the Eucharistic transubstantiation is merely a consequence of its anterior application to the doctrine of the immortality of the soul. As I explained in the preceding chapter, the Sacrament of the Eucharist is simply the reflection of the belief in immortality; it is, for the believer, the proof, by a mystical experience, that the soul is immortal and will enjoy God eternally. And the concept of substance was born, above all and before all, of the concept of the substantiality of the soul, and the latter was affirmed in order to confirm faith in the persistence of the soul after its separation from the body. Such was at the same time its first pragmatic application and its origin. And subsequently we have transferred this concept to external things. It is because I feel myself to be substance--that is to say, permanent in the midst of my changes--that I attribute substantiality to those agents exterior to me, which are also permanent in the midst of their changes--just as the concept of force is born of my sensation of personal effort in putting a thing in motion. Read carefully in the first part of the _Summa Theologica_ of St. Thomas Aquinas the first six articles of question lxxv., which discuss whether the human soul is body, whether it is something self-subsistent, whether such also is the soul of the lower animals, whether the soul is the man, whether the soul is composed of matter and form, and whether it is incorruptible, and then say if all this is not subtly intended to support the belief that this incorruptible substantiality of the soul renders it capable of receiving from God immortality, for it is clear that as He created it when He implanted it in the body, as St. Thomas says, so at its separation from the body He could annihilate it. And as the criticism of these proofs has been undertaken a hundred times, it is unnecessary to repeat it here.