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

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

Oakeshott was horrified by this, and was also disturbed by the postwar British welfare state; this was the impetus for his denunciation of political rationalism.

From Salon • Jul. 1, 2023

I feared for you, dear blessed Ork—I feared your bloodless rationalism.

From "Grendel" by John Gardner

Related Words

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