From Chapter 9 of Modern Man in Search of a Soul.

It was universally believed in the Middle Ages as well as in the Græco-Roman world that the soul is a substance. Indeed, mankind as a whole has held this belief from its earliest beginnings, and it was left for the second half of the nineteenth century to develop a “psychology without the soul”. Under the influence of scientific materialism, everything that could not be seen with the eyes or touched with the hands was held in doubt; such things were even laughed at because of their supposed affinity with metaphysics. Nothing was considered “scientific” or admitted to be true unless it could be perceived by the senses or traced back to physical causes. This radical change of view did not begin with philosophical materialism, for the way was being prepared long before. When the spiritual catastrophe of the Reformation put an end to the Gothic Age with its impetuous yearning for the heights, its geographical confinement, and its restricted view of the world, the vertical outlook of the European mind was forthwith intersected by the horizontal outlook of modern times. Consciousness ceased to grow upward, and grew instead in breadth of view, as well as in knowledge of the terrestrial globe. This was the period of the great voyages, and of the widening of man's ideas of the world by empirical discoveries. Belief in the substantiality of the spirit yielded more and more to the obtrusive conviction that material things alone have substance, till at last, after nearly four hundred years, the leading European thinkers and investigators came to regard the mind as wholly dependent on matter and material causation.

We are certainly not justified in saying that philosophy or natural science has brought about this complete volte-face. There were always a fair number of intelligent philosophers and scientists who had enough insight and depth of thought to accept this irrational reversal of standpoint only under protest; a few even resisted it, but they had no following and were powerless against the popular attitude of unreasoned, not to say emotional, surrender to the all-importance of the physical world. Let no one suppose that so radical a change in man's outlook could be brought about by reasoning and reflection, for no chain of reasoning can prove or disprove the existence of either mind or matter. Both these concepts, as every intelligent man today may ascertain for himself, are mere symbols that stand for something unknown and unexplored, and this something is postulated or denied according to man's mood and disposition or as the spirit of the age dictates. There is nothing to prevent the speculative intellect from treating the psyche, on the one hand, as a complicated biochemical phenomenon, and at bottom a mere play of electrons, or, on the other, from regarding the unpredictable behaviour of electrons as the sign of mental life even in them.

The fact that a metaphysics of the mind was supplanted in the nineteenth century by a metaphysics of matter, is a mere trick if we consider it as a question for the intellect; yet regarded from the standpoint of psychology, it is an unexampled revolution in man's outlook upon the world. Other-worldliness is converted into matter-of-factness; empirical boundaries are set to man's discussion of every problem, to his choice of purposes, and even to what he calls “meaning”. Intangible, inner happenings seem to have to yield place to things in the external, tangible world, and no value exists if it is not founded on a so-called fact. At least, this is how it appears to the simple mind.

It is futile, indeed, to attempt to treat this unreasoned change of opinion as a question of philosophy. We had better not try to do so, for if we maintain that mental phenomena arise from the activity of glands, we are sure of the thanks and respect of our contemporaries, whereas if we explain the break-up of the atom in the sun as an emanation of the creative Weltgeist, we shall be looked down upon as intellectual freaks. And yet both views are equally logical, equally metaphysical, equally arbitrary and equally symbolic. From the standpoint of epistemology it is just as admissible to derive animals from the human species, as man from animal species. But we know how ill Professor Daque fared in his academic career because of his sin against the spirit of the age, which will not let itself be trifled with. It is a religion, or — even more — a creed which has absolutely no connection with reason, but whose significance lies in the unpleasant fact that it is taken as the absolute measure of all truth and is supposed always to have common-sense upon its side.

The spirit of the age cannot be compassed by the processes of human reason. It is an inclination, an emotional tendency that works upon weaker minds, through the unconscious, with an overwhelming force of suggestion that carries them along with it. To think otherwise than our contemporaries think is somehow illegitimate and disturbing; it is even indecent, morbid or blasphemous, and therefore socially dangerous for the individual. He is stupidly swimming against the social current. Just as formerly the assumption was unquestionable that everything that exists takes its rise from the creative will of a God who is spirit, so the nineteenth century discovered the equally unquestionable truth that everything arises from material causes. Today the psyche does not build itself a body, but on the contrary, matter, by chemical action, produces the psyche. This reversal of outlook would be ludicrous if it were not one of the outstanding features of the spirit of the age. It is the popular way of thinking, and therefore it is decent, reasonable, scientific and normal. Mind must be thought to be an epiphenomenon of matter. The same conclusion is reached even if we say not “mind” but “psyche”, and in place of matter speak of brain, hormones, instincts or drives. To grant the substantiality of the soul or psyche is repugnant to the spirit of the age, for to do so would be heresy.

We have now discovered that it was intellectually unjustified presumption on our forefathers' part to assume that man has a soul; that that soul has substance, is of divine nature and therefore immortal; that there is a power inherent in it which builds up the body, supports its life, heals its ills and enables the soul to live independently of the body; that there are incorporeal spirits with which the soul associates; and that beyond our empirical present there is a spiritual world from which the soul receives knowledge of spiritual things whose origins cannot be discovered in this visible world. But people who are not above the general level of consciousness have not yet discovered that it is just as presumptuous and fantastic for us to assume that matter produces spirit; that apes give rise to human beings; that from the harmonious interplay of the drives of hunger, love, and power Kant's Critique of Pure Reason should have arisen; that the brain-cells manufacture thoughts, and that all this could not possibly be other than it is.

What or who, indeed, is this all-powerful matter? It is once more man's picture of a creative god, stripped this time of his anthropomorphic traits and taking the form of a universal concept whose meaning everyone presumes to understand. Consciousness today has grown enormously in breadth and extent, but unfortunately only in spatial dimensions; its temporal reach has not increased, for were that the case we should have a much more living sense of history. If our consciousness were not of today only, but had historical continuity, we should be reminded of similar transformations of the divine principle in Greek philosophy, and this might dispose us to be more critical of our present philosophical assumptions. We are, however, effectively prevented from indulging in such reflections by the spirit of the age. It looks upon history as a mere arsenal of convenient arguments that enables us, on occasion, to say: “Why, even old Aristotle knew that.” This being the state of affairs, we must ask ourselves how the spirit of the age attains such an uncanny power. It is without doubt a psychic phenomenon of the greatest importance — at all events a prejudice so deeply rooted that until we give it proper consideration we cannot even approach the problem of the psyche.

As I have said, the irresistible tendency to account for everything on physical grounds corresponds to the horizontal development of consciousness in the last four centuries, and this horizontal perspective is a reaction against the exclusively vertical perspective of the Gothic Age. It is a manifestation of the collective mind, and as such is not to be treated in terms of the consciousness of individuals. Resembling in this the primitives, we are at first wholly unconscious of our actions, and only discover long afterwards why it was that we acted in a certain way. In the meantime, we content ourselves with all sorts of rationalised accounts of our behaviour, all of them equally inadequate.

If we were conscious of the spirit of the age, we should know why we are so inclined to account for everything on physical grounds; we should know that it is because, up till now, too much was accounted for in terms of the spirit. This realisation would at once make us critical of our bias. We should say: most likely we are now making as serious an error on the other side. We delude ourselves with the thought that we know much more about matter than about a “metaphysical” mind, and so we overestimate physical causation and believe that it alone affords us a true explanation of life. But matter is just as inscrutable as mind. As to the ultimate we can know nothing, and only when we admit this do we return to a state of equilibrium. This is in no way to deny the close connection of psychic happenings with the physiological structure of the brain, with the glands, and the body in general. We are once for all deeply convinced of the fact that the contents of consciousness are to a large part determined by our sense-perceptions. We cannot fail to recognise that unalterable characteristics of a physical as well as a psychic nature are unconsciously ingrained in us by heredity, and we are deeply struck by the power of the instincts which inhibit or reinforce or otherwise modify our mental capacities. Indeed, we must admit that as to cause, purpose and meaning, the human psyche — however we approach it — is first and foremost a close reflection of everything we call corporeal, empirical and mundane. And finally, in the face of all these admissions, we must ask ourselves if the psyche is not after all a secondary manifestation — an epiphenomenon — and completely dependent upon the body. In the light of reason and of our commitments as practical men to an actual world, we say yes. It is only our doubts as to the omnipotence of matter which could lead us to examine in a critical way this verdict of science upon the human psyche.