Mathematical intuitionism

Intuitionism, also known as constructivism, is an approach to mathematics in which mathematical theorems are proven by the construction of the mathematical object whose existence is asserted.

Constructive mathematics is opposed to classical mathematics, in which it is perfectly legal to prove an object exists by assuming it does not and deriving a contradiction. Such proofs are called 'non-constructive'. Formally, inuititionistic mathematics is equal to classical mathematics, but without the logical law of the excluded middle.

The Dutch mathematician [L.E.J. Brouwer]? is considered the father of intuitionism.

Although few mathematicians nowadays can be regarded intuitionists, a constructivist proof is considered superior to a non-constructivist proof of the same theorem.