Full Idea
The essential problem is to explain how thinking manages reliably to preserve truth; and Associationism, as Kant rightly pointed out to Hume, hasn't the resources to do so.
Gist of Idea
Associationism can't explain how truth is preserved
Source
Jerry A. Fodor (Concepts:where cogn.science went wrong [1998], Ch.1)
Book Reference
Fodor,Jerry A.: 'Concepts: where cognitive science went wrong' [OUP 1998], p.10
A Reaction
One might be able to give an associationist account of truth-preservation if one became a bit more externalist about it, so that the normal association patterns track their connections with the external world.