Full Idea
For an intuitionist a mathematical statement is rendered true or false by a proof or disproof, that is, by a construction, and constructions are effected in time.
Gist of Idea
For intuitionists it is constructed proofs (which take time) which make statements true
Source
Michael Dummett (Elements of Intuitionism [1977], p.336), quoted by Shaughan Lavine - Understanding the Infinite VI.2
Book Reference
Lavine,Shaughan: 'Understanding the Infinite' [Harvard 1994], p.168
A Reaction
Lavine is quoting this to draw attention to the difficulties of thinking of it as all taking place 'in time', especially when dealing with infinities.