1. Criteriology, or a treatise on the motives of certitude, investigates the value of our faculties as means of acquiring knowledge and determines the ultimate criterion of certitude. -- It would be of little use to the intellect to have ideas and sensible images if it were not certain that these corresponded to objective reality. Hence, after Ideology has determined how the intellect forms its ideas and acquires its cognitions, Criteriology shows: 1. That the faculties by which we know afford us certain knowledge; 2. That there is an ultimate principle, which constitutes a solid foundation of the certitude of our knowledge.
ART I. -- THE COGNITIVE FACULTIES.
2. The cognitive faculties are: 1. the senses; 2. the intellect, including consciousness and reason. -- We know two kinds of objects, viz., sensible and intelligible. The senses perceive the sensible; the intellect, the intelligible. When the intellect is considered as having for its object the soul and its affections, or the internal facts of the soul, it is called consciousness; when it is considered as inferring one truth from another, it is called reason.
ART. II. -- THE VERACITY OF THE SENSES.
3. Sensation, considered as a modification of the sentient subject, is not an illusion but a reality. -- This is a primary fact which cannot reasonably be called in question. To say that the soul is in a state of illusion as to its own sensation is equivalent to asserting that it feels a sensation when there is no sensation, or that it feels when there is nothing to feel, which is a contradiction in terms. Sensation considered as representative of something else may be regarded as a mere representation of an object, or as participating in the nature of a judgment. Considered in the former way, sensation cannot deceive us as to the disposition of the sense, since it does not judge but only perceives; and perception, from its very nature, cannot disagree with the thing perceived, though it may occasion error in the intellect as to the disposition of objects. Considered in the second way, the senses are veracious, as will be established in the following paragraphs.
4. The senses, when in their normal state and exercised upon their proper sensible object, cannot deceive us. -- No cognitive faculty can be deceived in regard to its proper object, when the conditions required for the exercise of the power are fulfilled; otherwise, it would be a power that could effect nothing, which implies a contradiction. These conditions are (1) that the faculty be in its normal state, (2) that the proper object be suitably disposed, (3) that the medium between the faculty and the object be not modified. But if only one sense be exercised upon a common sensible, i. e., upon a quality that is perceived by several senses together, then error may arise, since an integral power is not directed to the object. An accidental sensible, i. e., the substance which supports the sensible qualities, demands, in addition to sense, the action of intellect.
5. The errors arising from the senses are not properly attributable to the senses, but to the intellect. -- Error is found only in the judgment; but the senses do not judge; therefore, the senses, properly speaking, do not deceive us. When they are diseased, or when any cause modifies or impairs the sensation, the senses cannot but receive the sensation so modified or impaired, and transmit it as they receive it to the intellect. Hence the intellect should not be precipitate in judging, and should take into account any abnormal conditions under which the sensation may be produced.
6. The Idealism of Berkeley is absurd; it admits no reality but that of spirits. -- The senses operating in their normal condition cannot deceive us; but the senses attest the existence of bodies; therefore, bodies really exist.
ART. III. -- THE VERACITY OF CONSCIOUSNESS.
7. The veracity of consciousness is a primary fact, which is affirmed even when it is doubted or denied. -- He who doubts or denies the veracity of consciousness either does not know that he doubts or denies it, and therefore cannot say that it deceives him; or else he does know that he doubts or denies the veracity of consciousness. But then, by what other faculty does he know this than by consciousness, the only witness of the internal facts of the soul? Therefore, he makes use of consciousness to deny consciousness, and is guilty of evident contradiction.
8. It is absurd to hold with Transcendental philosophers, that the testimony of consciousness is a mere illusion. -- The ancient Sceptics never questioned the veracity of consciousness; the German Transcendental philosophy alone has dared to do so, and it has thus arrived at absolute Scepticism. According to Fichte, "Reality all merges into a marvellous dream, without life to dream about or spirit to dream -- a dream which is gathered up into a dream of itself." But if our life is a dream, if the existence of spirit is an illusion, there must be a subject which dreams or which is under illusion. And this subject must, by the very consciousness by which it knows that it dreams, know also a spirit, which pronounces as an illusion the knowledge of the spirit that dreams. Thus the contradiction of the system is evident. Moreover, since Fichte denies all reality but the Ego, he makes consciousness essentially impossible; for every cognition requires three realities, the knower, the known, and the relation between them.
ART. IV. -- THE VERACITY OF INTELLECT AND REASON.
9. The intellect cannot deceive us in immediate judgments which relate either to the rational or to the experimental order. -- The intellect cannot be deceived in regard to its proper object, when this object is presented to it in such a way as to necessitate assent; otherwise, it could not know anything with certainty, and thus it would be a faculty unable to effect anything. Hence tbe intellect cannot be deceived in the perception of essences; nor can it be deceived in the cognition of first principles of either the rational or the experimental order. For these principles are self-evident: the former, because the attribute which is affirmed of the subject is found in the very idea of the subject; as, "The whole is equal to the sum of all its parts:" the latter, because they are only the expression of what this intellect sees distinctly in a sensible perception. Thus in the judgment, "The sky is blue," the intellect, by its abstractive power, separates blueness from the sky, and then predicates blue of the sky. Therefore, it is impossible for the intellect to be deceived in regard to first principles, whether rational or experimental.
10. Reason cannot deceive us in regard to conclusions easily deduced from first principles. -- The whole art of reasoning consists in deducing from two given or known judgments a third judgment, which is found to be contained in them. Hence there is a necessary connection between the conclusion and the premises. But if the truth of the conclusion is based on its necessary connection with the truth of the premises, reasoning evidently cannot deceive us, since a truth cannot both be and not be necessarily connected with another truth. Hence arises the repugnance which the intellect experiences to dissent from the conclusions which follow from a principle; also that secret displeasure which we feel when an adversary, having accepted certain principles, is unwilling to allow the conclusions which are logically drawn from them. But, on the other hand, when the conclusions are derived from a first principle only by long and intricate argumentations, the reason may be deceived, not because the reasoning in this case deceives, but because the natural weakness of the mind is such that it easily allows the attention to wander and thus overlooks some of the laws of reasoning.
11. The objection raised against the veracity of reason on account of the errors of philosophers only proves their abuse of reason. -- From the fact that the abuse of reason gives rise to error, we must not infer that reason cannot in any case apprehend truth with certainty. This affirmation of La Mennais (1782-1854) is contrary to good sense and sound logic. Error should be ascribed to lack of attention, to the violation of the laws of reasoning, by interweaving some fallacy with this operation, and to the abuse of reason; but not to the faculty itself, which by its natural act is never in fault.