In saying that the post-Aristotelian philosophers were not original thinkers, we must guard against the supposition that they contributed nothing of value to thought. On the contrary, while not putting forward any new theories, they generalised some of the principles borrowed from their predecessors, worked out others in minute detail, and stated the arguments on both sides of every controverted point with superior dialectic precision. Thus, while materialism had been assumed as self-evidently true by the pre-Socratic schools, it was maintained by the Stoics and Epicureans on what seemed to be grounds of experience and reason. And, similarly, we find that Plotinus, having arrived at the consciousness that spiritualism is the common ground on which Plato and Aristotle stand, the connecting trait which most completely distinguishes them from their successors, proceeds in his second essay[436] to argue the case against materialism more powerfully than it had ever been argued before, and with nearly as much effect as it has ever been argued since.
V.
Our personality, says the Alexandrian philosopher, cannot be a property of the body, for this is composed of parts, and is in a state of perpetual flux. A man’s self, then, is his soul; and the soul cannot be material, for the ultimate elements of matter are inanimate, and it is inconceivable that animation and reason should result from the aggregation of particles which, taken singly, are destitute of both; while, even were it possible, their disposition in a certain order would argue the presence of an intelligence controlling them from without. The Stoics themselves admit the force of these considerations, when they attribute reason to the fiery element or vital breath by which, according to them, all things are shaped. They do, indeed, talk about a certain elementary disposition as the principle of animation, but this disposition is either identical with the matter possessing it, in which case the difficulties already mentioned recur, or distinct from it, in which case the animating principle still remains to be accounted for.
Again, to suppose that the soul shares in the changes of the body is incompatible with the self-identity which memory reveals. To suppose that it is an extended substance is incompatible with its simultaneous presence, as an indivisible whole, at every point to which its activity reaches; as well as with the circumstance that all our sensations, though received through different organs, are referred to a common centre of consciousness. If the sensorium is a fluid body it will have no more power of retaining impressions than water; while, if it is a solid, new impressions will either not be received at all, or only when the old impressions are effaced.
Passing from sensation to thought, it is admitted that abstract conceptions are incorporeal: how, then, can they be received and entertained by a corporeal substance? Or what possible connexion can there be between different arrangements of material particles and such notions as temperance and justice? This is already a sufficiently near approach to the language of modern philosophy. In another essay, which according to the original arrangement stands third, and must have been composed immediately after that whence the foregoing arguments are transcribed, there is more than an approach, there is complete coincidence.[437] To deduce mind from atoms is, says Plotinus, if we may so speak, still more impossible than to deduce it from the elementary bodies. Granting that the atoms have a natural movement downwards, granting that they suffer a lateral deflection and so impinge on one another, still this could do no more than produce a disturbance in the bodies against which they strike. But to what atomic movement can one attribute psychic energies and affections? What sort of collision in the vertical line of descent, or in the oblique line of deflection, or in any direction you please, will account for the appearance of a particular kind of reasoning or mental impulse or thought, or how can it account for the existence of such processes at all? Here, of course, Plotinus is alluding to the Epicureans; but it is with the Stoic and other schools that he is principally concerned, and we return to his attack on their psychology.
The activities of the soul are thought, sensation, reasoning, desire, attention, and so forth: the activities of body are heat, cold, impact, and gravitation; if to these we add the characteristics of mind, the latter will have no special properties by which it can be known. And even in body we distinguish between quantity and quality; the former, at most, being corporeal, and the latter not corporeal at all. Here Plotinus just touches the idealistic method of modern spiritualism, but fails to follow it any further. He seems to have adopted Aristotle’s natural realism as a sufficient theory of external perception, and to have remained uninfluenced by Plato’s distrust of sensible appearances.
After disposing of the Stoic materialism, according to which the soul, though distinct from the body, is, equally with it, an extended and resisting substance, our philosopher proceeds to discuss the theories which make it a property or function of the body. The Pythagorean notion of the soul as a harmony of the body is met by a reproduction of the well-known arguments used against it in Plato’s Phaedo. Then comes the Aristotelian doctrine that the soul is the entelechy—that is to say, the realised purpose and perfection—of the physical organism to which it belongs. This is an idea which Aristotle himself had failed to make very clear, and the inadequacy of which he had virtually acknowledged by ascribing a different origin to reason, although this is counted as one of the psychic faculties. Plotinus, at any rate, could not appreciate an explanation which, whatever else it implied, certainly involved a considerable departure from his own dualistic interpretation of the difference between spirit and matter. He could not enter into Aristotle’s view of the one as a lower and less concentrated form of the other. The same arguments which had already been employed against Stoicism are now turned against the Peripatetic psychology. The soul as a principle, not only of memory and desire, but even of nutrition, is declared to be independent of and separable from the body. And, finally, as a result of the whole controversy, its immortality is affirmed. But how far this immortality involves the belief in a prolongation of personal existence after death, is a point which still remains uncertain. We shall return to the question in dealing with the religious opinions of Plotinus.
Closely connected with the materialism of the Stoics, and equally adverse to the principles of Plato and Aristotle, was their fatalism. In opposition to this, Plotinus proceeds to develop the spiritualistic doctrine of free-will.[438] In the previous discussion, we had to notice how closely his arguments resemble those employed by more modern controversialists. We have here to point out no less wide a difference between the two. Instead of presenting free-will as a fact of consciousness which is itself irreconcilable with the dependence of mental on material changes, our philosopher, conversely, infers that the soul must be free both from the conditions of mechanical causation and from the general interdependence of natural forces, because it is an individual substance.[439] In truth, the phenomena of volition were handled by the ancient philosophers with a vagueness and a feebleness offering the most singular contrast to their powerful and discriminating grasp of other psychological problems. Of necessarianism, in the modern sense, they had no idea. Aristotle failed to see that, quite apart from external restraints, our choice may conceivably be determined with the utmost rigour by an internal motive; nor could he understand that the circumstances which make a man responsible for his actions do not amount to a release of his conduct from the law of universal causation. In this respect, Plato saw somewhat deeper than his disciple, but created fresh confusion by identifying freedom with the supremacy of reason over irrational desire.[440] Plotinus generally adopts the Platonist point of view. According to this, the soul is free when she is extricated from the bonds of matter, and determined solely by the conditions of her spiritual existence. Thus virtue is not so much free as identical with freedom; while, contrariwise, vice means enslavement to the affections of the body, and therefore comes under the domain of material causation.[441] Yet, again, in criticising the fatalistic theories which represent human actions as entirely predetermined by divine providence, he protests against the ascription of so much that is evil to so good a source, and insists that at least the bad actions of men are due to their own free choice.[442]
In vindicating human freedom, Plotinus had to encounter a difficulty exceedingly characteristic of his age. This was the astrological superstition that everything depended on the stars, and that the future fate of every person might be predicted by observing their movements and configurations at the time of his birth. Philosophers found it much easier to demolish the pretensions of astrology by an abstract demonstration of their absurdity, than to get rid of the supposed facts which were currently quoted in their favour. That fortunes could be foretold on the strength of astronomical calculations with as much certainty as eclipses, seems to have been an accepted article of belief in the time of Plotinus, and one which he does not venture to dispute. He is therefore obliged to satisfy himself with maintaining that the stars do not cause, but merely foreshow the future, in the same manner as the flight of birds, to the prophetic virtue of which he also attaches implicit credence. All parts of Nature are connected by such an intimate sympathy, that each serves as a clue to the rest; and, on this principle, the stars may be regarded as the letters of a scripture in which the secrets of futurity are revealed.[443]
How much originality there may be in the anti-materialistic arguments of Plotinus we cannot tell. He certainly marks a great advance on Plato and Aristotle, approximating, in this respect, much more closely than they do to the modern standpoint. The indivisibility and permanence of mind had, no doubt, been strongly insisted on by those teachers, in contrast with the extended and fluctuating nature of body. But they did not, like him, deduce these characteristics from a direct analysis of consciousness as such. Plato inferred the simplicity and self-identity of mind from the simplicity and self-identity of the ideas which it contemplates. Aristotle went a step further, or perhaps only expressed the same meaning more clearly, when he associated immateriality with the identity of subject and object in thought.[444] Moreover, both Plato and Aristotle seem to have rested the whole spiritualistic case on objective rather than on subjective considerations; although, as we have seen, the subjective interest was what dominated all the while in their thoughts. Starting with the analogy of a living body, Plato argues, both in the Phaedrus and in the Laws, that soul must everywhere be the first cause of motion, and therefore must exist prior to body.[445] The elaborate scientific analysis of Aristotle’s Physics leads up to a similar conclusion; and the ontological analysis of the Metaphysics starts with the distinction between Form and Matter in bodies, to end with the question of their relative priority, and of the objective machinery by which they are united. Plotinus, too, sometimes refers to mind as the source of physical order; but this is rather in deference to his authorities than because the necessity of such an explanation seemed to him, as it did to them, the deepest ground of a spiritualistic philosophy. On the other hand, his psychological arguments for the immateriality of the soul are drawn from a wider area of experience than theirs, feeling being taken into account no less than thought; instead of restricting himself to one particular kind of cognition for evidence of spiritual power, he looks for it in every manifestation of living personality.