The human race is endowed with certainty as a quality annexed to life, a spontaneous result of the development of the soul's faculties. Certainty is natural; consequently it precedes all philosophy, and is independent of the opinions of men. For the same reason the question of certainty, although important to the knowledge of the laws to which our mind is subject, is, and always will be, unproductive of practical results. It is a dividing line fixed by reason lest at any time something should descend from the realm of abstraction prejudicial to society or individuals. Thus from its first investigations, philosophy forms a kind of alliance with good sense; they mutually promise never to be hostile to each other.
When we examine the foundations of certainty a question arises upon the first principle of human cognitions: does it exist, and what is it?
This question may have a double meaning. It may either mean a primitive truth containing all others, as the seed does plants and fruits; or simply a resting-point. The former gives rise to the question of transcendental science; the latter is the cause of the disputes in the schools on the preference of different truths in relation to the dignity of first principle.
If truth exists, there must be means of knowing it, hence the question of the value of criteria.
There is in the order of being one truth, the origin of all truths, God, who is also in the absolute intellectual order the origin of all truths. In the human intellectual order there is no one truth, the origin of all others; neither is there in the real, nor in the ideal order. The philosophy of the me can be of no account in establishing transcendental science. The doctrine of absolute identity is an absurdity; besides, it explains nothing.
The problem of representation is here proposed. The representation may be of identity, causality, or ideality. The last is founded on the preceding, but is distinct from it.
Besides the problem of representation we examined that of immediate intelligibility, a difficult problem, but one of the greatest importance to a perfect knowledge of the world of intelligences.
The disputes on the value of different principles, as to which has the right to be called fundamental, originate in a confusion of ideas. We attempt to compare things of very diverse orders, whereas this is impossible. Descartes' principle is the enunciation of a simple fact of consciousness; that of contradiction, an objective truth, the indispensable condition of every cognition: that of the Cartesians is the expression of a law of our mind. The three, each in its own way and sphere, are necessary; no one of them is totally independent of the others; the ruin of any one destroys our intelligence.
We have various criteria; but they may all be reduced to three: consciousness, or internal sense, evidence, and intellectual instinct, or common sense. Consciousness embraces all facts intimately present to our soul as purely subjective; evidence extends to all objective truths, upon which our reason is exercised; intellectual instinct is the natural inclination to assent in cases which lie without the domain of consciousness and evidence.
The intellectual instinct obliges us to give an objective value to ideas; in this case it mingles with the truths of evidence, and is, in ordinary language, confounded with evidence.
When the intellectual instinct operates upon non-evident objects and inclines us to assent, it is called common sense.
Consciousness and the intellectual instinct constitute the other criteria.
The criterion of evidence includes two things: the appearance of ideas, which belongs to consciousness; the objective value, existing or possible, which belongs to the intellectual instinct.
The testimony of the senses also has two parts: sensation as purely subjective, and this pertains to consciousness; and the belief in the objectiveness of sensations, and this pertains to the intellectual instinct.
The testimony of human authority is composed of that of the senses, which place us in relation with our fellow-men, and that of the intellectual instinct, which induces us to believe them.
Not everything is susceptible of proof; but every criterion stands the test of reason. The criterion of consciousness is a primitive fact of our nature; in that of evidence we discover the indispensable condition of the existence of reason itself; in that of the intellectual instinct by which we make our ideas objective, is found a law of our nature likewise indispensable to the very existence of reason; in that of common sense, properly so called, is the instinctive assent to truths, which, when examined, are seen to be perfectly reasonable; in that of the senses, and in that of human authority, we discover the same thing as in the other cases of common sense, which is a means of satisfying the necessities of sensation, intellectual, and moral life.
The criteria do not conflict with, but mutually aid and confirm each other. Neither is reason at war with nature, nor nature with reason; both are necessary to us; both direct us with certainty, although they are both liable to err, since they belong to a limited and very feeble being.
338. The philosophy which considers man only under a single aspect is incomplete, and in danger of becoming false. So far as certainty is concerned, we must bear in mind this last observation: to become excessively exclusive is to place one's self on the brink of error. We may analyze if we will the sources of truth; but we must not lose sight of their connection when examining them separately. To begin by conceiving a system, and then making everything conform to its demands, is to place truth in the bed of Procrustes. Unity is a great good; but we must be satisfied with the measure imposed upon us by nature. We must seek truth by human means, and in proportion to our capacity. The faculties of our soul are subject to certain laws, which we cannot abstract.
One of the most constant laws of our being is the necessity of a simultaneous exercise of our faculties, not only in order to become certain of truth, but even to discover it. Man joins the greatest multiplicity with simplicity: his soul is one, is endowed with various faculties, and united to a body of such variety and complication as to be called with much reason a little world. His faculties are in intimate and mutual relation; they exert a continuous influence upon each other. To isolate them is to mutilate, and sometimes to extinguish them. This remark is important, for it indicates the radical vice of all exclusive philosophy.
If a man have no sensations, his understanding has no materials, nor has it that stimulus, without which it remains dormant. When God united our soul and body, it was that one might aid the other; wherefore he established that admirable correspondence between the impressions of the body and the affections of the soul, which, therefore, needs the body as a medium, as an instrument, whether the action of the body upon it be supposed to be a true action, or only a simple occasion of causality of a higher order.
If a man, having no sensations, were to think, he would only think as a pure spirit; he would not be in relation with the external world, nor would he be a man in the sense in which we use this word. In such a case the body is superfluous, and there is no reason why it should be united to the soul.
If we admit sensations, and abstract reason, man is converted into a brute. He feels, but does not think: he experiences impressions, but does not combine them, for he is incapable of reflecting. Every thing succeeds in him as a series of necessary, isolated phenomena, which indicate nothing, lead to nothing, and are nothing but affections of a particular being who does not comprehend them, nor render to himself an account of them. It is even difficult to say of what kind are his relations with the external world. Arguing from appearances and analogy, it is probable that brutes also make their sensations objective; but ordinarily, their objectiveness differs from ours. Let us take sleep for example. If brutes sleep, and they probably do sleep, as certain appearances seem to indicate, it would not be strange should they not distinguish as we do between waking and sleeping.
This supposes some reflection upon acts, some comparison between the order and constancy of some, and the disorder and inconstancy of others; a reflection which man makes even in infancy, and continues to make all his life without adverting to it. When we awake from a deep sleep, we sometimes remain for several moments in doubt if we are asleep or awake: this doubt alone supposes a comparative reflection of the two states. What do we do in order to resolve this doubt? We examine