By soul is meant the principle of life in a living body - that which makes it alive. Further, it is the principle of the different activities characteristic of a living thing. In that wide sense, philosophers from ancient times have applied the word soul not only to the human soul but also to the life principle in all living bodies. In that sense, a tree or a horse has a soul.
We are concerned here with the human soul which has the powers of nutrition, growth and generation found in vegetative life, and the powers of sensitive knowledge and love possessed by animal life. We have, for example, sight, hearing, touch, taste, and smell - and so do cats or dogs or horses. Imagination and memory are also found in animals below man.
Mere matter cannot explain these attributes, for they transcend purely material powers; they demand as their cause something more than the common forces of matter. The vital principle responsible for them is called the soul.
But we also exercise activities higher than these. We have a higher kind of knowledge than cats or dogs - intellectual knowledge, by which we penetrate into the nature of things. No sense can do this; a superior power is needed. Sight, hearing and the other senses show only the superficial qualities of things, and if we could get no further than this the human race would never have developed science or culture. But we are able to use sense knowledge to go deeper, to see, however imperfectly, into the nature of things.
The intellect transcends the whole material order when it knows spiritual realities, and establishes the existence of God and something of His nature. As St Paul says: "[E]ver since the creation of the world his [God's] invisible nature, namely his eternal power and deity, has been clearly perceived in the things that have been made" (Romans 1:20).
Man also has will, which is the power of loving that transcends the appetites had by lower animals. Things we understand are seen as good or bad, and can be chosen or rejected. The power that does this is the will, and because it follows intellectual knowledge, it too must be a power surpassing the appetites we have in common with the lower animals. A property of the will is freedom, which is why we are responsible for our actions and deserve praise or blame.
A thing is understood from what it does, so some understanding of the human soul can be gained by examining its activities of understanding and willing.
Take the concept brought to mind by the word circle. It expresses the nature of this figure, but without any of the concrete particulars that characterise any existing circle. For instance, an existing circle may be ten centimetres across and drawn in white chalk. But the idea of circle abstracts from these particulars, and expresses the common nature possessed by all circles.
Similarly the idea of man fits every member of the human race, while abstracting from all the particulars, such as height, skin colour, weight, possessed by individuals.
But a power (intellect), which can know things without the material conditions had by individuals, must be superior to material things. If it can know immaterially, it must be immaterial, because what it can do is based on what it is.
Similarly, the will makes choices based on intellectual knowledge, transcending the appetites we have in common with the lower animals. Often, in fact, the will struggles against those sense appetites. As St Paul puts it: "For I delight in the law of God, in my inmost self, but I see in my members another law at war with the law of my mind" (Romans 7:23).
These two powers, intellect and will, surpass in their activity the capability of the material world - their acts are spiritual, not material. So the being that exercises them must be at least part spirit. Clearly we are not pure spirits, like angels, for much of our activity essentially involves the body. But the human soul does more than animate the body; it has acts proper to itself and is itself spirit, not a merely material principle.
Survival of soul
It follows that the human soul survives death. Material things are made up of parts that can be separated, resulting in death. But a spirit is immune from dissolution because it is not made of elements that disintegrate. And since the powers of the intellect and will are in the soul, they will operate after death. This conclusion from philosophy is confirmed by Revelation, as in St Paul's wish to be separated from the body and to be with the Lord (II Cor 5:8).
But the separated soul, after death, is in an unnatural state, for man is essentially a compound of soul and body. The soul should not be thought of as a complete being which happens to dwell in the body during this earthly life.
Aristotle aptly compares the unity between body and soul to that between wax and the shape given it by a stamp (Aristotle: De anima, book 2, chapter 1). The result is not wax plus shape (as though they were two things), but shaped wax. And a human being is not a soul plus a body, but an ensouled body.
Based on this fact, a strong argument from reason can be given for a resurrection of the body: God acts wisely and treats things according to their nature, so it seems he would raise our bodies, making us once more complete human beings. From Revelation we know this to be a fact: all will rise at the end of time, and will continue, body and soul, for all eternity.
John Young is a Melbourne-based Catholic author, writer and lecturer.