 On such interpretation, the question concerning the validity of LEM is then equivalent to the question of the possibility of unsolvable (mathematical) problems (Brouwer 1908, translated in Heyting (ed) 1975): LEM should then fail because it is doubtful that for any mathematical statement \(\phi\), either there is a proof of \(\phi\) or a proof of \(\neg  \phi\).[1] 