An effort is necessary in order clearly to perceive what the facts of consciousness are, and what its testimony is; for without this it is impossible to advance one step in the investigation of the first principle of human knowledge. Confusion on this point makes us fall into transcendental equivocations. We shall hereafter have occasion to observe this, and we have already encountered lamentable examples of such deviations in the errors of the philosophy of the me.
152. Evidence is usually called an intellectual light. This is a very happy metaphor, and even exact; but, like all metaphors, it has the defect of being of but little service to explain the mysteries of philosophy. We also find intellectual light in many acts of consciousness. There is also a sort of clear light in that intimate presence by which an operation or an impression is offered to the mind; it shines upon the eye of the soul, and makes it see what is before it. If, then, we define evidence only by calling it the light of the intellect, we confound it with consciousness, or, at least, by the use of ambiguous language, give others occasion of confounding them.
Let us not be thought to blame those who have used the metaphor of light, or to flatter ourselves with being able to define evidence with all exactness; for who can express in words this phenomenon of our mind? If we are to have any metaphor, that of the intellectual light seems to be the most adequate. For, in truth, when we fix our attention upon evidence, in order to examine its nature and its effects on the mind, it very naturally presents itself under the image of a light, whose splendor illumines the objects, and enables the mind to contemplate them: but this, we repeat, is not enough. We will, then, although we do not undertake exactly to define it, point out a mark to distinguish it from every thing else.
153. Evidence is always accompanied by the necessity, and consequently, by the universality, of the truths which it attests. There is no evidence of the contingent, except in so far as subjected to a necessary principle.
Let us explain this doctrine by comparing examples taken respectively from consciousness and evidence.
That there is in me a being which thinks, I know, not by evidence, but by consciousness. That whatever thinks exists, I know, not by consciousness, but by evidence. In both cases the certainty is absolute, irresistible; but in the first it rests upon a particular, contingent fact; in the second upon a universal and necessary truth. That I think is certain for me, but not necessarily so for others; the disappearance of my thought does not overturn the world of intelligences; if my thought should now cease to exist, truth in itself would suffer no change; other intellects might and would continue to perceive truth; and neither in the real nor in the ideal order would there be less concert and harmony.
I ask myself if I think, and in the bottom of my soul I read that I do think: I ask myself if this thought is necessary, and not only does experience tell me that it is not, but I can find no reason why it should be necessary. Even supposing that my thought ceases to exist, I perceive that I continue to reason in due form. Thus I examine what would have happened if I had not existed, or what may hereafter happen if I cease to exist; and I assent to principles and draw conclusions without transgressing any law of the intellect. The ideal world and the real world are presented to my eyes as a magnificent spectacle at which I indeed assist, but from which I may withdraw without the representation undergoing any change, except that I should leave vacant the imperceptible place which I now occupy. But it is very different with the truths which are the object of evidence. It is not necessary for me to think; but it is so necessary for whatever thinks to exist, that no efforts of mine could suffice to abstract this necessity for one moment. If, taking an absurd position, I suppose the contrary, and imagine for an instant the relation between thought and being to be cut short, I break the chain which supports the order of the entire universe; every thing is reversed, thrown into confusion; and I know not if what I see be chaos or nonentity. What has taken place? The intellect has only suffered a contradiction, at the same time affirming and denying thought, because it affirmed a thought to which it denied existence. It has violated a universal and absolutely necessary law, the violation of which throws every thing into chaos. Not the certainty of the soul's existence, supported by the testimony of consciousness, suffices to prevent the confusion: the intellect by contradicting itself has denied itself; from its insensate words, not being, but nonentity has resulted, not light, but darkness; and this darkness cast over whatever exists or is possible turns back upon it and involves it in eternal night.
154. We have here fixed and defined the conditions of consciousness and evidence. The object of the former is the individual, the contingent; that of the latter the universal and the necessary. Only in God, the source of all truth, the universal and necessary principle of being and of knowledge, is consciousness identified with evidence; and it is not possible to abstract the testimony of his consciousness, without annihilating everything. What would remain in the world were I to disappear? the creature asks itself, and answers: everything except myself. Were God to ask himself this question, he would answer: nothing.
155. We have given the name of intellectual instinct to the impulse which in many cases produces certainty without the aid of the testimony either of consciousness or of evidence. If you show a man a target, then blindfold his eyes, and turn him around at random several times, and, after this, place a bow in his hands, and assure him that the arrow will strike the precise centre of the target, he will say that this is impossible; and nothing can induce him to believe so great an absurdity. And why not? Because of the testimony of consciousness? No! For the question is now of external objects. Neither does he depend on evidence; for the objects of evidence are things necessary, and it is not intrinsically impossible for the arrow to hit the mark assigned. On what then rests his profound conviction that this is not possible? If we suppose him to know nothing of theories, of probabilities, and combinations, to have no knowledge of this science, and never to have so much as thought of such things, his certainty is just as great as it would be were he able to base it upon some sort of calculation. All the bystanders, whether rude or cultivated, ignorant or learned, need no reflection to be equally certain; all will say, or think, "this is impossible; it cannot happen." We again ask, what is the foundation of so strong a conviction? Not springing from consciousness, or from either mediate or immediate evidence, it manifestly can have no other origin than that internal force which we call intellectual instinct, and which may be called common sense, or anything else, so long as the fact itself is recognized. It is a precious gift, which the Creator has given to us, to make us reasonable even before we reason, and to enable us rightly to govern our conduct when we lack time to examine motives of prudence.
156. This intellectual instinct embraces many objects of different orders; it is the guide and the shield of reason: the guide, because it precedes and shows the way; the shield, because it defends reason from her own cavils, and because sophistry becomes dumb in its presence.
157. The testimony of human authority, equally necessary to the individual and to society, commands our assent, by means of an intellectual instinct. Man believes man, believes society, even before thinking of the motives of his faith; few examine them at all, and yet this faith is universal.
We do not here inquire if intellectual instinct sometimes deceives, or why, or in what cases it deceives; at present we only seek to establish its existence; and with regard to the errors to which it leads, we shall simply remark, that in a weak being, such as man, the rule is continually changing, and as it is not possible to find a man good, without any admixture of evil, so is it impossible to find truth without some admixture of error.
158. We make sensations objective only by virtue of an irresistible instinct. Nothing is more certain, more evident to the eyes of philosophy, than the subjectivity of all sensations; that is, sensations are immanent phenomena, are within us, and do not go out of us; and yet nothing is more constant than the transition made by the whole human race from the subjective to the objective, from the internal to the external, from the phenomenon to the reality. On what is this transition grounded? If the most eminent philosophers experienced so much difficulty in finding the bridge, which unites the two opposite banks; if some of them, wearied with investigation, resolutely asserted that it was not possible to discover it, will the commonalty of mankind discover it from their very childhood? Evidently, motives of reasoning do not explain the transition; appeal must be made to the instinct of nature. There is then an instinct, which by