  In 1949, Brouwer (1949A) publishes the first of a new class of strong counterexamples, a class that differs from Brouwer’s earlier strong counterexample (1928, see above) in that the type of argument, which now goes by the name of “creating subject argument”, involves essential reference to the temporal structure of the creating subject’s mathematical activity (Heyting, 1956, chs. III and VIII; van Atten, 2003, chs.4 and 5; van Atten, 2018).