Founded by L.E.J. Brouwer, Brouwers intuitionism is a metaphysical stance where mathematics is a “languageless” activity of the mind based on the intuition of inner time. For Brouwer, mathematics is a human mental activity, fundamentally languageless, grounded in the intuition of time.
For Brouwer, mathematical agreement is not secured by language alone, nor by direct comparison of private mental states, but by one mathematician’s linguistic expression enabling another to carry out the same construction for themselves.