Reasoning

REASONING. - From ratio (v. RAGIONE), it is the act by which thought, by virtue of given propositions, facts, judgments, passes to a new affirmation. R. is therefore, in its broadest meaning, synonymous with inference, and indicates the "discourse" or movement of reason from knowledge in act (premises, προτάσεις, τὰ προτεινόμενα) to further judgments (conclusions), having with those a nexus of causal derivation. The logical nexus of derivation ("consequenti" in scholastic terminology) is essential, so that not every process of thought accomplished by chance discovery or by simple succession in time can be called r.

In traditional logic, r. is, alongside the concept (v.) and the judgment (v.), the third fundamental activity of reason. St. Thomas recognizes in it the distinctive character of human understanding, essentially analytic and progressive in time: «homines ad intelligibile veritatem cognoscendam perveniunt procedendo de uno ad aliud ... et ideo rationales dicuntur» (Sum. Theol., 1°, q. 79, a. 8, c.; cf. De verit., q. 15, a. 1). Nevertheless, the knowing principle that understands (intellectus) and that reasons (ratio) is identical; the diversity and multiplicity is merely functional: whereas the intellect denotes «pura apprehensio veritatis», it is proper instead to reason «discurrere ab uno in aliud, ut per id quod est notum deveniat in cognitionem ignoti» (In anal. post., I, lect. 1, n. 4; cf. Sum. Theol., loc. cit., and q. 85, a. 4). R. is therefore, in relation to intellection, as "acquisition" to "attainment", "becoming" to "being", "motion" to "rest". Analyzing this relationship, St. Thomas observes that, just as movement is not possible without a fixed point of departure, so too r. presupposes certain truths or principles of immediate intuition («intellectus principiorum») from which it starts and to which it returns in the resolutive and demonstrative process of conclusions. The «ratio» therefore finds in the «intellectus» its principle and its term: «intellectus invenitur rationis principium quantum ad viam inveniendi, terminus vero quantum ad viam iudicandi» (De verit., q. 15 a. 1).

As inference, r. is an essentially active function of thought: not pure intuition of a given, but a process of inquiry («a certis ad incertorum indagationem nitens cogitatio»; St. Augustine, De immort. anim., cap. 1: PL 32, 1021 A). It is clear, however, that the intuitive moment is not absent from r. and indeed assumes in it more complex forms than in the pure concept. R. in fact is accomplished through a precise noetic act in which a certain proposition B is seen to depend on and derive from a preceding proposition or series of propositions A. R. is therefore intuition-affirmation of judgments (relations between concepts) and of causal nexuses between judgments: it thus involves multiple intuitive moments that make r. almost a synthesis of the other mental acts, and by which the indicated distinction between «intellectus» and «ratio» is further attenuated.

R. as inference does not necessarily imply the discovery of new truths, as in the case of a proposition already known, derived (proved) from a principle that justifies or confirms it (for example: theft is an evil because it is irreconcilable with social living, and society is a good for man). The novelty of r. (which in reality is always present, otherwise it would not be possible to speak of true inference or rational process) consists often precisely in the proof: B was known as problematic; now it is seen in its connection with A, which is certain: r. here determines the relation of derivation of B from A and thus arrives at a new certainty and evidence of B (even if it was perhaps already known by another route).

With regard to the various forms of inference (for which see SILLOGISMO), the general division of r. into deduction (v.) and induction (v.) should be noted here. While deduction verifies the type of formal, logically necessary inference (to which the norm «ex vero non sequitur nisi verum» principally refers: cf. Aristotle, Anal. pr., II, cap. 2, 53 b 7), in induction, on the other hand, the inference from particular truths to universal principles is founded, more than on the logical structure of r., on the intellectual intuition of the relation of particular facts to the ontological determination of universal nature. But it would be an arbitrary restriction to understand r. solely as formal inference (cf. A. Lalande, op. cit. in bibl., p. 868), since induction too verifies an actual process and dialectic of thought. Equally unjustified, on the other hand, is the contrary assertion (cf. J. Stuart Mill, A system of logic, II, cap. 3) that sees a true inference only in induction, in the sense of an amplification and extension of knowledge.

R. as a process in time (and therefore open to a true "progress" of knowledge; for Bosanquet the denial of the temporal duration of inference «is the first and fatal error» [op. cit. in bibl., p. 4]) and as dialectical development, is an essential form of rational thought. It is a function, on the one hand, of the fragmentariness and analyticity of human knowing, and on the other, of the indefinite relations that bind into unity the object and the contents of thought. Movement of knowledge toward unity, analysis toward synthesis, r. is the logical expression of the ontological organicity of the real. Hence a perfection and power of thought which, while extending in breadth the domain of truth, at the same time clarifies it in depth, determining its multiple internal relations of structure, necessity and cause.

Ugo Viglino