There are different kinds of formal logic: propositional, first order, second order, modal, fuzzy, .... What kinds of formal logic have applications in law? Thanks.

  • 6
    None whatsoever. You might find a passing reference to Aristotelian syllogisms.
    – user6726
    Jun 10, 2023 at 14:33
  • 2
    I’m voting to close this question because it belongs on philosophy.stackexchange.com Jun 11, 2023 at 0:35
  • 3
    @BlueDogRanch I think this is a perfect question about law. It is actually somewhat a disturbing revelation that logic has no place in law — contrary to what many lay people may think.
    – Greendrake
    Jun 12, 2023 at 5:29

3 Answers 3


The Life of the Law Has Not Been Logic; It Has Been Experience.

-- Oliver Wendell Holmes, Jr.

Basically none.


The common law is tolerant of much illogicality, especially on the surface; but no system of law can be workable if it has not got logic at the root of it.

(Lord Devlin, Hedley Byrne & Co., Ltd v Heller & Partners [1964] AC 465, 516)

To think like a lawyer, you need to use three types of logical reasoning:

However, the standard required is not rigorous logical proof, it is reasonableness. That is, on the evidence provided, is it open to a reasonable person to draw the conclusions that the decision maker made.


The words Blackacre and Greenacre and the like, used in the way lawyers use them, are examples of what mathematical logicians call "bound variables."

  • "I wonder whether there may be some reason for the downvotes here other than ignorance of logic among those learned in law? Can someone explain?" I did not downvote, but I am explaining some issues with this answer. Jun 16, 2023 at 13:08

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