One may theoretically ask whether the world of science, the world that appears to us, is exactly the real world, existing outside of us. It is thus that in the philosophy of Kant the famous question as to the thing in itself is stated. But it is equally certain that in the name of that philosophy this question ought logically to be discarded. One is astonished that the author of the Critique of Pure Reason did not immediately close that door opened to scientific scepticism. After his critique, in fact, it is evident that that substratum which some are forced to imagine as a support to phenomena—that the indeterminate and indeterminable substance that they represent beneath the forms and qualities of things,—is both a non-being and nonsense. Das Ding an sich ist ein Unding. (The thing in itself is an unthing.) It is a remnant of ancient metaphysics which ought to be eliminated from modern philosophy. In allowing it to introduce itself into our theory of knowledge, it overturns it as would a heterogeneous element. He that persists in distinguishing between the thing in itself and the phenomenal thing will never be able to give an account of the objectivity of the sciences of Nature, and of the kind of certitude that belongs to them.

That which appears to us from without is not doubtless all the reality of the world; but it is a real world. By his calculations, Leverrier came first to suspect the existence of a large planet as yet unperceived; then he came to measure its volume, to trace its orbit, and finally to mark its place at a given time. He said to his brother astronomers: "Look there!" and the planet appeared at the end of their telescopes.

How explain, moreover, without this reality of science, the power that science gives to man over Nature? His power, is it not always exactly in proportion to his knowledge?

In what then does this objectivity of science consist if it is not founded on the pretended knowledge of the thing in itself? In the necessary link that scientific thought establishes between phenomena. This necessity does not come from experience, for it is something ideal, which our mind adds to all experience. But, as we can only think according to these necessary laws, we necessarily objectivise in all scientific study. We thus affirm, of necessity, the fundamental unity of the laws of thought and the laws of phenomena. Experience always confirms this immediate affirmation. Now this necessity, it is objectivity itself; it is the only noumenon that we are authorised to seek behind phenomena in Nature, and behind the manifestations of pure reason in spirit.

The first effect of this objective necessity is to eliminate from the work of science the feelings and the subjective will of the ego. A thinking and acting subject is no doubt necessary in making science; but the characteristic of science is to see what it studies apart from the subject, apart even from the psychical phenomena that it observes in the ego itself. Posited outside the ego, the laws that it promulgates appear to us therefore independent of it. This elimination of the subject from the conclusions of science thus becomes the sign and the measure of their objectivity. Where the elimination is complete, as in astronomy and physics, the objectivity is entire. On the contrary, history, e.g. where the elimination can never be absolute, always tends towards objectivity, but never reaches it.

It is altogether otherwise with religious knowledge. With it we enter at once into the subjective order—that is to say, into an order of psychological facts, of determinations and internal dispositions of the subject itself, the succession of which constitutes his personal life. To eliminate the ego would not here be possible; for this would be both to eliminate the materials and to dry up the living spring of knowledge. An ancient illusion pretended that we know God, as we know the phenomena of Nature, and that the religious life springs from that objective knowledge as by a sort of practical application. The very opposite is true. God is not a phenomenon that we may observe apart from ourselves, or a truth demonstrable by logical reasoning. He who does not feel Him inside his heart will never find Him outside. The object of religious knowledge only reveals itself in the subject, by the religious phenomena themselves. It is with the religious consciousness as with the moral consciousness. In this the subject feels obliged, and this obligation itself constitutes the revelation of the moral object which obliges us. There is no good known outside that. The same in religion: we never become conscious of our piety without—at the same time that we feel religiously moved—perceiving, more or less obscurely, in that very emotion the object and the cause of religion, i.e. God.

Observe the natural and spontaneous movement of piety: a soul feels itself to be trusting, that it is established in peace and light; is it strong, humble, resigned, obedient? It immediately attributes its strength, its faith, its humility, its obedience, to the action of the Divine Spirit within itself. Anne Doubourg, dying at the stake, prayed thus: "O God, Do not abandon me lest I should fall off from Thee." The prophet of Israel said: "Turn me, O Lord, and I shall be turned." And the father in the Gospels cried: "Lord, I believe; help Thou mine unbelief." To feel thus in our personal and empirical activity the action and the presence of the Spirit of God within our own spirit, is the mystery, but it is also the source, of religion.

It will be seen how much religious knowledge and the science of Nature differ by their very origin. The one is the theory of the receptive and logical life of the ego; the other is the theory of its active and spontaneous life. As both the receptive and the active life are one, however, the two orders of knowledge are neither isolated nor independent. But they must never be confounded. Their results will always remain heterogeneous; they are not of the same order, and cannot supply the place of each other. If you were to admit, e.g., that philosophers may succeed (as they have often been believed to do) in establishing a veritable objective science of God, and if they were thus to know God in Himself and apart from the religious ego, that scientific knowledge of God, even if it were possible, would not be religious knowledge; for to know God religiously is to know Him in His relation to us—that is to say, in our consciousness, in so far as He is present in it and determines it towards piety. This is the sense in which it is permissible to maintain that religion is as independent of metaphysics as it is of cosmology. It is the same with the knowledge of the world. To know the world as an astronomer or a physicist is not to know it religiously. To know it religiously is, while taking it as it is, and in no wise contradicting the scientific laws according to which it is governed, to determine its value in relation to the life of spirit; it is to estimate it according as it is a means, a hindrance, or a menace, to the progress of that life. In the same way, to know ourselves religiously is not to construct scientific psychology; but that psychology being once constructed, and properly constructed, it is to realise ourselves in our relation both to God and to the world, forcing ourselves to surmount the contradictions from which we suffer, in order that we may attain to unity and peace of mind. Thus, not only can religious knowledge never cast off its subjective character; it is in reality nothing but that very subjectivity of piety considered in its action and in its legitimate development.

The inner nature of these two orders of knowledge having been defined, it becomes evident that each of them is valid in its own domain, and that they cannot legitimately encroach upon each other. To try to establish by religious faith the reality of any phenomenon whatsoever, of which experimental science or intellectual criticism are the sole judges; or to wish to formulate by means of objective science a moral judgment which springs from the subjective consciousness—these are two equivalent encroachments and abuses. Experimental science has the right to forbid the religious consciousness to do violence to it; but the religious consciousness has an equal right to restrict science to its true limits. We must prevent confusion if we would put an end to the conflicts between them. To enclose God in any phenomenal form is, properly speaking, superstition or idolatry; to confine or dissipate the soul in external phenomenism, and to deny the seriousness and value of its religious and moral activity, is infidelity, properly so called.

Truths of the religious and moral order are known by a subjective act of what Pascal calls the heart. Science can know nothing about them, for they are not in its order. In the same way the phenomena of Nature are only known and measured by observation and calculation. Neither the heart nor religious faith can decide with respect to them. Each order has its certitude. We must not say that in the one the certitude is greater than in the other. Science is not more sure of its object than moral or religious faith is of its own; but it is sure in a different way. Scientific certitude has at its basis intellectual evidence. Religious certitude has for its foundation the feeling of subjective life, or moral evidence. The first gives satisfaction to the intellect; the second gives to the whole soul the sense of order re-established, of health regained, of force and peace. It is the happy feeling of deliverance, the inward assurance of "salvation."