Consciousness, evidence, and intellectual instinct or common sense, are the three means; to which correspond truths of consciousness, necessary truths, and common-sense truths. These are distinct, different, and in many cases unconnected with each other; and he, who seeks to acquire complete and accurate ideas upon matters relating to the first principle of human knowledge, must mark out their limits with great care.
148. That means which we have called consciousness, or the intimate sense of that which passes within us, that which we experience, is independent of all the others. Destroy evidence, destroy intellectual instinct, yet consciousness remains. In order to feel, and to be sure that we feel, and what we feel, we need only experience. If we suppose the principle of contradiction to be doubtful, still it will not shake our certainty that we suffer when we suffer, that we rejoice when we rejoice, that we think when we think. The presence of the act, or the impression at the bottom of our soul, is intimate, immediate to us, and of irresistible efficacy to place us above all doubt. Sleeping or waking, sane or insane, the testimony of consciousness is the same; there may be an error in the object, but there can be none in the internal phenomenon. The lunatic who believes that he counts numberless bags of dollars, certainly does not count them, and in this he is deceived; yet he has in his mind the consciousness of what he does, and in this he is infallible. A man who dreams that he has fallen into the hands of robbers, is deceived as to the external object, but not as regards the act by which he believes it.
Consciousness is independent of all extrinsic testimony; its necessity is inevitable, its force irresistible in producing certainty; it is infallible in what concerns only itself; if it exist it must give testimony of itself; if it does not exist it cannot give it. In it reality and appearance are confounded; it cannot be apparent without being real; the appearance alone is already a true consciousness.
149. We include in the testimony of consciousness all that which we experience in our soul, all that which affects what some call the human me, ideas, thoughts of every class, acts of the will, sentiments, sensations; in a word, every thing of which we can say: I experience it.
150. Manifestly the truths of consciousness are rather facts to be pointed out, than combinations to be enunciated. This is not to say that they cannot be enunciated, but that in themselves they abstract all intellectual form, are simple elements, in ordering and comparing which the intellect may occupy itself, but which of themselves give no light, represent nothing, but only present what they are; that they are mere facts, beyond which we cannot go.
151. The habit of reflecting upon consciousness, and of joining purely intellectual operations with facts of simple internal experience, makes it difficult to conceive this isolation, in which every thing purely subjective is by its nature found. We endeavor to abstract reflection, but we reflect upon our very effort to abstract it. Our intellect is a fire, which, extinguished on one side, burns on the other; the very effort to extinguish it ordinarily makes it burn brighter. Hence the difficulty of distinguishing the two characters of purely subjective and purely objective, to mark the dividing line between evidence and consciousness, between the known and the experienced. Nevertheless, the separation of two such different elements may be made easy, by considering that brutes are, in their own way, conscious of what they inwardly experience; not supposing them to be mere machines, we must allow them consciousness, or the intimate presence of their sensations. Without this even sensation is inconceivable, for that can have no sensation which does not perceive that it feels. Brutes reflect not on what passes within themselves; they experience it, but nothing more. Sensations succeed one another in their soul, connected only by the unity of the being experiencing them; but they do not take them for objects and consequently, do not combine or transform them in any manner; they leave them as they are, simple facts. From this we may derive some light for the conception of what the simple facts of consciousness are in us when abandoned to themselves, perfectly isolated, separated from purely intellectual operations, and under no subjection to reflective activity, which, combining them in various ways, and elevating them to the region of the purely ideal, presents them to us in such a manner as to make us forget their primitive purity.
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.