Full Idea
The Input Objection says a pure coherence theory would seem to allow that a system of beliefs be justified in spite of being utterly out of contact with the world it purports to describe, so long as it is, to a sufficient extent, coherent.
Gist of Idea
A purely coherent theory cannot be true of the world without some contact with the world
Source
Erik J. Olsson (Against Coherence [2005], 4.1)
Book Reference
Olsson,Erik J.: 'Against Coherence' [OUP 2008], p.62
A Reaction
Olson seems impressed by this objection, but I don't see how a system could be coherently about the world if it had no known contact with the world. Olson seems to ignore meta-coherence, which evaluates the status of the system being studied.