Reason
Collier's New Encyclopedia (1921)
in logic, the premise or or premises of an argument, and especially the minor premise. In In metaphys- n ics, the power of thinking consecutively; the power of passing in mental review all the facts and principles bearing on a subject, and, after a careful consideration of their bearings, drawing conclusions in many cases conformable with truth. Reason, weighing facts, discovers the law of gravitation, calculates eclipses, weighs the planets, ascertains the constituent elements of the sun, and even of more distant worlds. It can exercise itself on the most abstract and spiritual theories, as well as on those of a simpler character. Reid distinguished between reason and judgment, considering the sphere of the former to be propositions capable of demonstration. Stewart considered the word reason as ambiguous. In common discourse it denotes the power of discriminating truth from falsehood, and right from wrong. To these he adds the power of devising to accomplish ends; or reason means may be limited to the power of distinguishing truth from falsehood; or it may be used of our rational power in general, or of the discursive faculty alone. Brown thinks that there is no faculty of reason which is nothing more . Imthan a series of relative suggestions manuel Kant's "Critique of Pure Reason" appeared in 1781. Mill considers reasoning in its extended sense to be synonymous with inference, and divides it into induction, i. e., reasoning from particulars to generals, and ratiocination, reasoning from generals to particulars. Formerly it was believed that of the whole visible creation man alone was capable of reasoning; but Darwin considers that only a few persons now dispute that animals possess some power of reason. Their actions may be due to instinct or to the association of ideas, the last named principle being connected with reason. In history: On Nov. 10, 1793, the French National Convention ordered the worship of the Goddess of Reason. Madame Maillard. selected as such a goddess, was drawn on a splendid car to the cathedral of Notre Dame to receive homage from the multitude. For some time afterward that cathedral was designated the Temple of Reason.
What Has Changed in the Last Century
Collier's in 1921 could still frame reason largely as the philosophers had left it — Reid, Dugald Stewart, Kant's "Critique of Pure Reason" of 1781, and Mill's split of inference into induction and ratiocination. What has since transformed the subject is the empirical study of how people actually reason: from the 1960s onward, work such as Peter Wason's selection task and Amos Tversky and Daniel Kahneman's research on heuristics and biases showed that ordinary human inference departs systematically from logical norms, a line of work that won Kahneman the 2002 Nobel prize in economics. Formal logic meanwhile hardened into mathematics and then into machinery — Gödel's incompleteness theorems of 1931 set limits on what deduction can prove, and automated reasoning now underpins computer science. The entry's cautious note that Darwin thought "animals possess some power of reason" has been settled emphatically in Darwin's favour by studies of tool use and problem-solving in crows, chimpanzees and octopuses.
Written for this edition, 2026.