Full Idea
How else, other than via some form of representational system, could a human organism contain information as a content over which it could operate or 'attitudinise'?
Gist of Idea
Propositional attitudes require representation
Source
William Lyons (Approaches to Intentionality [1995], Intro)
Book Reference
Lyons,William: 'Approaches to Intentionality' [OUP 1998], p.4
A Reaction
Depends what you mean by 'representational'. In its vaguest sense, this is just a tautology - content must be held in the mind in some form or other, but that tells us nothing.