A note on evolution
It does not follow, however, that this order proceeds, as it were, from the simplest to the most complex and thus evolution is not self-evident, precisely because there exist differences between things which are so fundamental that the evidence requires a different principle of operation in the one and in the other: a difference of such a kind that one must, while recognising common characteristics to all life, recognise different kinds of life, different kinds of form which animate 'first matter' or which in some other sense exist.
Therefore one could speak of an evolution from the simple to the complex only if it did not imply the evolution of animal life into human life, precisely because animal life and human life are, considered precisely as forms of life, fundamentally different.
This understanding of things does not deny the existence of common characteristics of these forms of life; indeed, in general, it is the existence of these common characteristics that make the discussion possible.
But it does confine the possibility of evolution to the evolution of the body of a creature whose existence doesn't exceed, of itself, the capacities of such a process - unless, as in the case of man, it were to lead to but not include the possession of a rational soul782.
Otherwise one is asserting the general principal that a process can manifest an actuality that it didn't already possess as an actuality.
In other words, if matter inherently possesses the actuality of being the total human being, then it is by definition already the development of a human being and not the development of a human being from a kind of matter without this actuality.
But if all matter possessed this actuality then it would all be human and, therefore, capable of what human beings are capable.
This is obviously not the case as matter, of itself, does not possess the power to understand.
Therefore the theory of evolution implies, for it own coherence, the necessity of an account of the origin of human understanding as distinct from the development of the body it purports to explain.
The one in three 'form' of life
If the soul is by definition the form of the body, then in the technical sense previously articulated, this raises the following question: if the soul is the form of the body then in what sense if any is the soul the life of the body?
This is because it is precisely as a form that the soul is what it is, namely, that which animates the body.
Now it is precisely this which is not self-evident in the sense that if the soul is, simply, the life of the body, then why has it been so difficult to explain it to the point where it can be said the question is answered?783
In other words, how can the soul be the form of the body when the time at which it becomes so is so uncertain784, and has even given rise to the idea of delayed animation, that is, of there being first a vegetative soul, then an animal soul and then, finally, a rational soul with all the powers of the previous souls?785
Perhaps the answer is that the soul is precisely the life of the body, that is, the soul is the life of what we call the body and not of anything else.
Thus it is necessary to define the body if one is going to say in what sense the soul is the life of the body.
For the life that the soul is to the body is not identical to the fundamental form of life that is characteristic of all physical things as existing, namely the movements which occur as characteristic of all existing matter: the movements of the particles in the atoms which are basic to all physical matter.
The human soul is, therefore, not necessary to the life of the body absolutely, if what is meant by that is the soul's animation of absolutely everything that the body is as physical matter.
For if that were true then at death there would not only be the end of the body's life, but the end of the fundamental activity of all its matter.
In other words, as I've already said, the soul is the life of the body as body.
But besides the sub-atomic movements of matter is the movement of the sperm.
This again is something which, from the point of view of the soul's animation of the body, is already in movement and is already, therefore and to that extent biologically alive and is already, therefore, something which the soul as immediately made by God does not need to animate, except in the sense the sperm is of the living man, as indeed the egg is of the living woman, and thus in that sense arises out of life: life transmitting human life.
The sperm is by definition of its movement, a true transmission786 of biologically alive human life.
In other words there is a characteristically human life, transmitted through the man, in the form of the life of the sperm which, by definition, is realized fully when the sperm animates the egg.
This form of life which is the animated activity of the sperm is again an existing activity with all its characteristics which the soul, as immediately created by God does not have to animate.
Therefore, while it is true that a man's sperm would not exist if he did not and is in that sense dependent on his existence precisely as a man, as it is also true the life of the sperm does, therefore, exist in some relation to the man's soul as the animating principle of his body, it is also true that as a form of life it is precisely in its capacity to transmit life that its own particular function lies.
In other words what is unique about the sperm lies in it being the living germ of human life.
This, however, gives a second component to the structure of human life, which, while not discontiuous with the first is already different from it and could be called the biological dimension of bodily life.
The choice of a third form of life is guided by three things.
Firstly, what appears to be the aforementioned natural distinctions, as it were, in the different kinds of activity fundamental to life.
Secondly, that St. Thomas Aquinas saw the possibility of three component forms of life constituting the human being, albeit that the three informed matter each in turn, and each one subsequent to the first included the capacity of the previous one, culminating in the final one of the rational soul.
Finally, his definition of the rational soul as non-corporeal787, immaterial and indeed spiritual788.
A third form of life would be, then, by definition what the first two could not of their nature give, such that it could be called the spiritual principal of human life; and nature is here defined as the inherent perameter to growth entailed in a particular form of life.
A working definition of the human being, then, that fits the facts, is that a human being is a unitary expression of the following three, diverse forms of life: the spiritual, the biological and the physical.
Finally, however, and for good reason, the Catholic Church has traditionally accepted the distinction between the spiritual and the corporeal as constituting the two orders of created reality which are, in man, one789.
Therefore this analysis of the human being does not propose a third division, as such, so much as looks at what is called corporeal in the light of modern science and as applied to the task of a philosophical understanding of what it is to be a human being.
Therefore the human being could be said to be composed790 of three, philosophically discerned forms of life, almost as if the human being is like a rope platted from these three forms of life.
The human being expresses, at its simplest level, the unity inherent in its diversity; and, it is at the same both an intra-personal and an inter-personal791 reality.
If this is both a real and therefore a philosophically sustainable unity of diverse forms of life, then its theological significance is that the human being is fashioned out of three forms of life, and is, therefore, in St. Augustine's expression, a "trace" of the Blessed Trinity in creation792.