rationalism

American  

[rash-uh-nl-iz-uhm] / ˈræʃ ə nlˌɪz əm /

noun

1. the principle or habit of accepting reason as the supreme authority in matters of opinion, belief, or conduct.

2. Philosophy.

   1. the doctrine that reason alone is a source of knowledge and is independent of experience.

   2. (in the philosophies of Descartes, Spinoza, etc.) the doctrine that all knowledge is expressible in self-evident propositions or their consequences.

3. Theology. the doctrine that human reason, unaided by divine revelation, is an adequate or the sole guide to all attainable religious truth.

4. Architecture.

   1. a design movement principally of the mid-19th century that emphasized the development of modern ornament integrated with structure and the decorative use of materials and textures rather than as added adornment.

   2. the doctrines and practices of this movement.

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rationalism British  

/ ˈræʃənəˌlɪzəm /

noun

1. reliance on reason rather than intuition to justify one's beliefs or actions

2. philosophy

   1. the doctrine that knowledge about reality can be obtained by reason alone without recourse to experience

   2. the doctrine that human knowledge can all be encompassed within a single, usually deductive, system

   3. the school of philosophy initiated by Descartes which held both the above doctrines

3. the belief that knowledge and truth are ascertained by rational thought and not by divine or supernatural revelation

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Other Word Forms

• antirationalism noun
• antirationalist noun
• antirationalistic adjective
• nonrationalism noun
• nonrationalist noun
• nonrationalistic adjective
• nonrationalistical adjective
• nonrationalistically adverb
• rationalist noun
• rationalistic adjective
• rationalistical adjective
• rationalistically adverb

Etymology

Origin of rationalism

First recorded in 1790–1800; rational + -ism

Explanation

Rationalism is a doctrine that prioritizes reason over emotion. If you're scared of the dark and convinced there's a monster in your closet, your parents will beg you to be rational, and rely on what you know (empty closet) instead of what you fear (monster!). French philosopher René Descartes, who wrote "I think therefore I am," is considered the father of rationalism. He believed that eternal truths can only be discovered and tested through reason. The "scientific method" is one of rationalism's great gifts to mankind––if something cannot be proven through a repeatable experiment, you do not consider it to be true.

Example Sentences

Maybe I’m betraying my hopeless rationalism, but if I learned of the reality of time travel and “aerial spirits,” I’d be a little more preoccupied by it than Iris seems to be.

From The Wall Street Journal • Mar. 5, 2026

This “consumption downgrade” is not a move toward poverty but toward a militant form of rationalism.

From MarketWatch • Jan. 27, 2026

A computer science major with an interest in rationalism, self-improvement and effective altruism — a philosophical movement that uses evidence and reason to help others — Mangione enthused about technological innovation.

From Los Angeles Times • Dec. 14, 2024

Prof Selove said: "This MA will allow people to re-examine the assumption that the West is the place of rationalism and science, while the rest of the world is a place of magic and superstition."

From BBC • Oct. 3, 2023

There is a puzzle here, because the standard alternative to voluntarism is rationalism, and a rationalist would hold that the laws of nature, like the laws of mathematics, exist because they are necessary.

From "The Invention of Science" by David Wootton

Related Words

• attitude
• doctrine
• idea
• ideology
• logic
• outlook
• reasoning
• system
• tenet
• theory
• thinking
• thought
• truth
• view
• viewpoint
• wisdom