Definition:A Priori (Logic)
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Definition
A priori knowledge is the sort of knowledge which comes from reason alone.
That is, it does not require the exercise of experience to know it.
Thus the truth value of a statement can be decided by a logical argument whose premises are definitions.
Examples
Probability
The following is an example of a priori reasoning:
- The probability of rolling a $6$ on a fair die is $\dfrac 1 6$.
The truth of the above statement is dependent upon:
- the definition of the term probability
- the definition of a fair die.
A Legal Statement
The following is an example of a priori reasoning:
- If Fred Bloggs has committed a crime, then he is guilty.
The truth of the above statement is dependent upon the definition of the term guilty, which, in natural language simply means having committed a crime.
Contrast this with:
- Fred Bloggs has committed the crime of usury
the truth value of which is dependent upon knowing whether or not he actually did it.
Also see
Linguistic Note
The phrase a priori derives from the Latin for from what comes before.
Sources
- 1989: Ephraim J. Borowski and Jonathan M. Borwein: Dictionary of Mathematics ... (previous) ... (next): a priori: 1.
- 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): a priori
- 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): a priori
- 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): a priori