UNIVERSAL CONSENT. — This is the general agreement of human thought concerning matters of fact and first principles of immediate evidence, or also concerning certain derived truths, particularly in the ethical-religious sphere. That such universal consent exists is itself an incontrovertible fact: amid the continual variation of human opinions, mentality, tastes, and tendencies, and despite the profound historical upheavals in the values of thought and life, human reason in its original spontaneity always proves consistent with itself in its fundamental evaluations of truth and goodness. The reason for this fact, attributed by fideism (T. Reid and his school, E. F. Jacobi) to an obscure instinct of nature, must instead be sought, as s. Tommaso expresses it (Sum. Theol., 1ª-2ª, q. 94, a. 2), in the fundamental inclination of spiritual nature toward the good proper to it, namely, truth, and therefore also in its natural capacity to attain II. The sensus naturae communis is nothing other than this natural inclination or tendency; and if one wishes to speak of instinct in the sense of a disposition inherent in nature, this is an instinct that is not without a certain self-awareness, in the light and certainty of intellectual knowledge, even if the objective reasons determining it may remain shrouded in darkness. Universal consent understood in this way must therefore not be confused with common convictions of various kinds, often erroneous, which sometimes accompany, even for the duration of historical epochs, the consciousness of peoples and civilizations, and originate in particular circumstances of fact, tradition, and environment—not, certainly, in the pure and spontaneous exercise of reason.
Universal consent was already regarded in ancient philosophy as an argument for certainty. Aristotle: « quod omnibus verum videtur, hoc dicimus esse » (Eth. Nicom., X, 2, 1173 a); Seneca: « multum dare solemus praesumptioni (προλήψει) omnium hominum; apud nos veritatis argumentum est aliquid omnibus videri » (Epist., 117); Cicero: « Omni autem in re consensio omnium gentium lex naturae putanda est » (Disp. tusc., I, 13); « De quo autem omnium natura consentit id verum esse necesse est » (De nat. deor., I, 17). In the last century F.-R. de Lamennais (v.) elevated universal consent, the « general reason », to the supreme criterion of certainty, to which every assertion of individual reason ought to be referred in order to escape the snares of doubt and recover the truth: « Common sense is the rule of every individual reason »; « outside it there is neither certainty nor truth nor reason » (Défense de l'essai sur l'indifférence en matière de religion, Paris 1821, pp. 571, 625).
Against this excessive evaluation by Lamennais, scholastic criteriology acknowledges that universal consent has, in relation to certainty, a positive but not primitive value. First of all, universal consent must be distinguished according as it concerns facts and principles of immediate evidence, or rather complex and derived truths: in the first case, it can claim apodictic value, not so much because it is a fact, even a universal one, but rather because of the theoretical presuppositions implied by the fact, namely, the value of reason itself and the objectivity of its fundamental laws. But insofar as it concerns derived truths—for example, the existence of God or the immortality of the soul—the agreement of the majority of human beings has merely a value of confirmation and of probability, more or less substantial, upon which philosophy, sustained and justified solely by its self-control, cannot in any way rely. In every case, universal consent absolutely cannot be taken as the primary foundation of certainty, which must be established not upon authority but upon the evidence critically attained by thought through the reflective examination of itself and of the totality of human experience.