EVIDENZA. — From e-videre (Gr. ἐνέργεια), in the general sense, it is the clarity and manifestation of truth. The etymological meaning of the word leads to a more precise determination of the real content of the concept; since the clarity of truth is ultimately nothing other than the necessity of judgment, e. may be defined as the objective necessity with which a judgment imposes itself upon thought. Everything, and only that, is evident which imposes itself upon the mind as necessarily thinkable (with absolute or hypothetical necessity), by virtue of its objective conceptual determination or of its concrete presentation in experience. Understood in this way, e., while always implying, as a relative concept, a relation to the knowing subject, nevertheless asserts itself as an essentially objective value.
It must therefore be distinguished both from certainty and from the clarity of perception (Cartesio), which may both be illusory and independent of the truth and necessity of the judgment. Likewise, and consequently, it is only in relation to intellectual knowledge that one can speak of e. in the proper sense; so-called empirical and aesthetic e. is formally not such, except insofar as the datum of sensible or aesthetic perception is taken up into the intellect’s assertive act, in which alone the formal value of truth is realized.
E. may be found both in first judgments (rational principles and intuitive judgments of fact) and in derived judgments; but in the latter e. too is mediated, insofar as it is obtained through the process of demonstration, which shows its connection with truths and principles evident
per se. One also speaks of intrinsic and extrinsic e., according as the necessity of the judgment is grasped in the relation itself between subject and predicate, or is instead known indirectly through the extrinsic value of authority (evidentia veritatis, evidentia auctoritatis). Only intrinsic e. is e. in the formal sense.
Traditional gnoseology, following Aristotle in this, as well as the Epicurean and Stoic schools and s. Tommaso, places in e. the universal criterion of certainty, in the sense that it is its necessary and sufficient condition. To know is in fact to perceive, to intuit: for this spiritual intuition to be possible, an indispensable condition is that the object disclose itself in its intelligibility to thought; and it is also a sufficient condition, because the mind cannot fail to assent as soon as it has grasped the intelligibility and truth of the object. Properly speaking, no further criterion is needed to distinguish true e. from so-called apparent e.: precisely because the latter does not posit itself as the absolute necessity or thinkability of the object, it can always be overcome through rigorous mental discipline and complete spiritual freedom that does not yield to movements of a purely subjective order.
It must nevertheless be observed that e., as a criterion of truth, cannot claim greater value than that entailed by the very notion of a criterion of truth (v. CRITERIO). Truth, because of the complexity of the forms and levels according to which it is distributed in human knowledge, depending on the corresponding complexity of objects, cannot be regulated by a single abstract and theoretical criterion. E. must therefore always be viewed and judged in the objective-subjective concreteness with which it presents itself in individual consciousness, where the subjective and relative factors of individual personalities often exert an influence to a greater or lesser degree. Thus, in concrete terms, e. comes to coincide, in a certain sense, with truth itself and is subject to the same requirements and apparent antinomies entailed, in some of its aspects, by the problem of truth (v.).