Full Idea
The fact that it seems possible to establish a sortal notion of direction by reference to lines and parallelism, discloses tacit commitments to directions in statements about parallelism...There is incoherence in the idea that a line might lack direction.
Gist of Idea
If we can establish directions from lines and parallelism, we were already committed to directions
Source
Crispin Wright (Frege's Concept of Numbers as Objects [1983], 4.xviii)
Book Reference
Wright,Crispin: 'Frege's Conception of Numbers' [Scots Philosophical Monographs 1983], p.148
A Reaction
This seems like a slippery slope into a very extravagant platonism about concepts. Are concepts like direction as much a part of the natural world as rivers are? What other undiscovered concepts await us?