Sentence:  Symbol structures can, and commonly do, serve as internal representations (e.g. "mental images") of the environments to which the symbol system is seeking to adapt. They allow it to model that environment with greater or less <WSD>veridicality</WSD> and in greater or less detail, and consequently to reason about it. 
Meaning of the word marked with <WSD> tags:  The degree to which something, such as a knowledge structure, is veridical; the degree to which an experience, perception, or interpretation accurately represents reality.