Observational

The essential fact is simply that all the pictures which science now draws of nature, and which alone seem capable of according with observational fact, are mathematical pictures.

An alternative way of defending the proposal to conflate NP MOVEMENT with XP MOVEMENT would be to question the observational adequacy of the claim that NP MOVEMENT only ever has NP constituents as its target.

No less than the novelist, the psychologist must employ techniques of literary construction to render scientific accounts acceptable. Most importantly, to the extent that such techniques dominate the scientific account, observational practices—regardless of rigor—cease to be influential.