intueri

Latin intueri combines in- (at, toward) and tueri (to look at, to watch). The word meant to gaze at, to contemplate, to look at something directly. Late Latin intuitio developed the sense of immediate apprehension — knowing something by looking at it directly rather than through a chain of reasoning. Thomas Aquinas used intuitio in the thirteenth century for the angels' way of knowing: direct, unmediated, without the laborious steps of human logic.

Descartes gave intuition a central role in his philosophy. For him, intuitio was the mind's clear and distinct perception of a truth — the intellectual equivalent of seeing something in bright light. The axioms of mathematics are grasped by intuition, not deduced. You do not prove that a triangle has three sides; you see it. Intuition, for Descartes, was not a vague feeling but the most reliable form of knowledge, more certain than any chain of deduction.

Kant complicated the picture in the Critique of Pure Reason (1781), distinguishing between intellectual intuition (which only God possesses) and sensible intuition (Anschauung), through which humans receive sensory data. For Kant, human intuition is always mediated by the forms of space and time — we never see things as they are, only as they appear. The directness that Latin intueri promised was, in Kant's system, an illusion.

Modern psychology split intuition from reason entirely. Daniel Kahneman's Thinking, Fast and Slow (2011) places intuition in System 1 — the fast, automatic, effortless mode of thought — and deliberation in System 2. Intuition is rapid pattern recognition, built from experience, often accurate but susceptible to systematic biases. The angelic knowing that Aquinas described has become a computational shortcut, powerful but fallible.