a priori

American  

[ey prahy-awr-ahy, -ohr-ahy, ey pree-awr-ee, -ohr-ee, ah pree-awr-ee, -ohr-ee] / ˌeɪ praɪˈɔr aɪ, -ˈoʊr aɪ, ˌeɪ priˈɔr i, -ˈoʊr i, ˌɑ priˈɔr i, -ˈoʊr i /

adjective

1. from a general law to a particular instance; valid independently of observation.

2. existing in the mind prior to and independent of experience, as a faculty or character trait.

3. not based on prior study or examination; nonanalytic.

   an a priori judgment.

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a priori British  

/ ˌeɪpraɪˈɒrɪtɪ, ɑː prɪˈɔːrɪ, eɪ praɪˈɔːraɪ /

adjective

1. logic relating to or involving deductive reasoning from a general principle to the expected facts or effects

2. logic known to be true independently of or in advance of experience of the subject matter; requiring no evidence for its validation or support

3. statistics See prior probability mathematical probability

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Usage

What does a priori mean? A priori is a term applied to knowledge considered to be true without being based on previous experience or observation. In this sense, a priori describes knowledge that requires no evidence. A priori comes from Latin and literally translates as “from the previous” or “from the one before.”It’s often applied to things involving deductive reasoning, which uses general principles to arrive at specific facts or conclusions (from cause to effect). It can be used as an adjective, as in a priori knowledge, or as an adverb, as in We shouldn’t assume a priori that this is true. A priori contrasts with a posteriori, which literally translates as “from the latter” or “from the one behind” and is applied to things that are based on experience, observation, or existing data. A posteriori is applied to things that involve inductive reasoning, which uses specific instances to arrive at a general principle or law (from effect to cause). Both a priori and a posteriori are used in the context of reasoning and philosophy, especially epistemology, which is the philosophical study of knowledge. Both can also be used generally, though they’re often used formally. Example: Any proposition considered to be a priori knowledge should be carefully examined for bias. ​

Other Word Forms

• apriority noun

Etymology

Origin of a priori

1645–55; < Latin: literally, from the one before. See a- ⁴, prior ¹

Compare meaning

How does a-priori compare to similar and commonly confused words? Explore the most common comparisons:

• a priori vs. a posteriori

Example Sentences

"Whether ultra-processed foods contribute to our currently rising rates of non-communicable disease requires direct testing in analytic studies designed a priori to do so," said Charles H. Hennekens, M.D.,

From Science Daily • Feb. 20, 2024

"I am not a priori against", he said.

From Reuters • Nov. 28, 2023

Among people who have good immune health, can I predict a priori that they will do as well during an infection?

From Scientific American • Jun. 21, 2023

While a priori knowledge does not require experience, this does not mean that it must always be reached using reason alone.

From Textbooks • Jun. 15, 2022

There are no a priori grounds for thinking that this is a good way to conduct intellectual life.

From "The Invention of Science" by David Wootton