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.

Is it possible for the unforewarned reason to conclude that our soul is a substance from the fact that our consciousness of our identity—­and this within very narrow and variable limits—­persists through all the changes of our body?  We might as well say of a ship that put out to sea and lost first one piece of timber, which was replaced by another of the same shape and dimensions, then lost another, and so on with all her timbers, and finally returned to port the same ship, with the same build, the same sea-going qualities, recognizable by everybody as the same—­we might as well say of such a ship that it had a substantial soul.  Is it possible for the unforewarned reason to infer the simplicity of the soul from the fact that we have to judge and unify our thoughts?  Thought is not one but complex, and for the reason the soul is nothing but the succession of co-ordinated states of consciousness.

In books of psychology written from the spiritualist point of view, it is customary to begin the discussion of the existence of the soul as a simple substance, separable from the body, after this style:  There is in me a principle which thinks, wills, and feels....  Now this implies a begging of the question.  For it is far from being an immediate truth that there is in me such a principle; the immediate truth is that I think, will, and feel.  And I—­the I that thinks, wills, and feels—­am immediately my living body with the states of consciousness which it sustains.  It is my living body that thinks, wills, and feels.  How?  How you please.