Full Idea
No proposition can be intelligible or consistent with regard to objects, which is not so with regard to perceptions.
Gist of Idea
A proposition cannot be intelligible or consistent, if the perceptions are not so
Source
David Hume (Treatise of Human Nature, + Appendix [1740], Appendix)
Book Reference
Hume,David: 'A Treatise of Human Nature', ed/tr. Selby-Bigge/Nidditch [OUP 1978], p.634
A Reaction
An interesting variant on expressions of the empiricist principle. Presumably one can say intelligible things about Escher drawings.