CERTAINTY, CERTITUDE (Certum, from cerno).— Personal assurance of reality, possessed in the exercise of immediate knowledge, or attained by the ingathering of sufficient evidence. Certain knowledge or certainty is the confidence with which the mind reposes in the information of its faculties. According to the mode in which it is attained, certainty is immediate by sense and intuition, and mediate by reasoning and demonstration. Self-consciousness reveals with certainty the different states and operations of our own minds. We cannot doubt the reality of what our senses clearly testify. Inference, strictly warranted by logical law, gives certainty. Reason reveals to us first truths with intuitive certainty.
| According to the grounds on which it rests, it is called— Physical, when it concerns truth which cannot be otherwise, according to the laws of nature; Metaphysical, when applied to truth which cannot be otherwise, such as the first principles of reason; Moral, when it involves truth expressed in law, which is an imperative of the life. |
In connection with the last of the three, popular usage has introduced «moral certainty» as a condensed expression applicable to conviction resting on moral evidence in default of direct evidence. In absence of proof of the actual occurrence, we may have moral evidence founded on the indications of motive on the part of the agent, and on collateral testimony from a variety of actions. Moral conviction may amount to the highest degree of probability, and to all practical purposes may be as influential as certainty. For it should be observed that probability and certainty are two states of mind, and not two modes of the reality. The reality is one and the same, but oar knowledge of it may be probable or certain. Probability has more or less of doubt, and admits of degrees. Certainty excludes doubt, and admits neither of increase nor diminution.
«Certain, in its primary sense, is applied (according to its etymology, from cerno) to the state of a person’s mind; denoting any one’s full and complete conviction; and generally, though not always, implying that there is sufficient ground for such conviction. It was thence easily transferred metonymically to the truths or events, respecting which this conviction is rationally entertained. And uncertain (as well as the substantives and adverbs derived from these adjectives) follows the same rule. Thus we say, ‘It is certain,’ &c, meaning that we are sure; whereas the fact may be uncertain and certain to different individuals. From not attending to this, the words uncertain and contingent have been considered as denoting some quality in the things themselves—and chance has been regarded as a real agent» (Whately, Logic, app. I.).— V. Locke’s Essay, bk. II. ch. VI. and bk. III. ch. IV.
«The criterion of true knowledge is not to be looked for anywhere abroad without our own minds, neither in the height above, nor in the depth beneath, but only in our knowledge and conception themselves » (Cudworth, Eternal and Immutable Mortality, bk IV. ch. V.).
«The holding of a thing to be true is a phenomenon in our understanding which may rest on objective grounds, but requires also subjective causes in the mind of the person judging. If a judgment is valid for every rational being, then its ground is objectively sufficient, and it is termed a conviction. If, on the other hand, it has its ground in the particular character of the subject, it is termed a persuasion» (Kant’s Critique of Pure Reason, Transc. Doct. of Method, ch. II. sec 3; Meiklejohn, 496; Max Müller, II. 703).
As regards the ground of certainty Protagoras and Epicurus in ancient times, and Hobbes and the modern sensationalists, have made Sense the measure and ground of certainty. Descartes and his followers founded it on self-consciousness, Cogito ergo sum; while others have received as certain only what is homologated by human reason in general.
Certainty is not the peculiar characteristic of knowledge furnished by any one faculty, but is the common inheritance of any or all of our intellectual faculties when legitimately exercised within their respective spheres. Though we are thus naturally and necessarily determined to accept the knowledge furnished by our faculties, our knowledge, according to Kant, cannot be proved to be absolute, or a knowledge of things in themselves as they must appear to all intelligent beings, but is merely relative, or a knowledge of things as they appear to us. Now, it is true that we cannot, as Kant has expressed it, objectify the subjective. Without rising out of human nature to the possession of a higher, we cannot sit in judgment on the faculties of that nature. But, admitting that our knowledge is relative, we are merely saying it is ours,—it is human,—it is according to the measure of a man,—it is attained by human faculties, and must be relative, bearing proportion to the faculties by which it is attained. We may not know all that can be known of the objects of our knowledge, but still, what we know, we do know,—we possess a veritable knowledge. The ground and encouragement of all inquiry is, that our faculties are fitted to apprehend the reality of things. Faith in their trustworthiness is spontaneous. Doubt concerning it is an after-thought. Scepticism as a creed is self-destructive. He who doubts is certain that he doubts. Omnis qui utrum sit veritas dubitat, in se ipso habet verum, unde non dubitet (Augustine, De vera Religione).
Etiam qui negat veritatem esse, concedit veritatem esse; si enim veritas non est, verum est, veritatem non esse (Thomas Aquinas, Sum. Theol.; S. Descartes, Method, pt. IV.).— V. EVIDENCE, CRITERION, KNOWLEDGE, PROBABLE.
