Full Idea
Brouwer regards as somehow 'wicked' the idea that mathematics can be applied to a non-mental subject matter, the physical world, and that it might develop in response to the needs which that application reveals.
Gist of Idea
Brouwer regards the application of mathematics to the world as somehow 'wicked'
Source
report of Luitzen E.J. Brouwer (Mathematics, Science and Language [1928]) by David Bostock - Philosophy of Mathematics 7.1
Book Reference
Bostock,David: 'Philosophy of Mathematics: An Introduction' [Wiley-Blackwell 2009], p.198
A Reaction
The idea is that mathematics only concerns creations of the human mind. It presumably has no more application than, say, noughts-and-crosses.