Full Idea
The materialist says: it is by means of a series of straight lines that one imagines the perfect straight line as an ideal limit. But the progression itself contains what is infinite. It is in relation to the straight that we say a line is less twisted.
Gist of Idea
We don't infer the straight from the twisted, because judging the twisted needs the straight
Source
Simone Weil (Lect 1: Materialist Viewpoint [1933], p.87)
A Reaction
This is the platonist response to my preferred view that the mind produces all the pure concepts such as idealisations. I prefer to refer to pulling a rope, where the straight emerges as an obvious observed limit.
Book Reference
Weil,Simone: 'Lectures on Philosophy' [CUP 1978], p.87