Full Idea
Epistemology is a big worry for structuralists. ..To conjecture that something has a particular structure, we must already have conceived of the idea of the structure itself; we cannot be discovering structures by conjecturing them.
Gist of Idea
To see a structure in something, we must already have the idea of the structure
Source
James Robert Brown (Philosophy of Mathematics [1999], Ch. 4)
Book Reference
Brown,James Robert: 'Philosophy of Mathematics' [Routledge 2002], p.59
A Reaction
This has to be a crucial area of discussion. Do we have our heads full of abstract structures before we look out of the window? Externalism about the mind is important here; mind and world are not utterly distinct things.