Reason

Reason (Latin ratio; Greek lógos and noûs; German Vernunft) — The faculty of thinking, arguing, and knowing by principles, traditionally taken as the distinguishing trait of human beings and as a criterion of truth and right action. Latin ratio translates Greek logos, which means at once word, calculation, proportion, and ground. Heraclitus already saw in the logos the order governing the cosmos; Plato, in the Republic, assigns the rational part of the soul the rule over the others; Aristotle defines the human being as an animal possessing logos (Politics, I, 2) and distinguishes theoretical reason, directed at what is necessary, from practical reason, directed at action (see nous and phronesis). In modern rationalism, Descartes opens the Discourse on Method (1637) by affirming that good sense, the power of judging well and distinguishing true from false, is equal in all men. Hume reacts with the thesis that reason “is, and ought only to be the slave of the passions” (Treatise of Human Nature, II, 3, 3), limiting it to comparing ideas and inferring matters of fact. Kant, in the Critique of Pure Reason (1781), distinguishes understanding (Verstand), the faculty of concepts applied to experience, from reason (Vernunft), the faculty of principles that tends to exceed the bounds of the possible, and adds practical reason as the source of the moral law. Hegel makes reason the principle of the real and of its history. In the twentieth century, Horkheimer (Eclipse of Reason, 1947) criticizes the reduction of reason to instrumental reason, and Habermas proposes communicative reason. See rationalism, Enlightenment, Kant, Descartes, and Hume.

← Glossary