Full Idea
In the traditional empiricist picture, we go about modal enquiry by trying to see whether we can imagine a situation in which it would be correct to assert the negation of a proposed necessary truth. Thus we can find out the limits of our concepts.
Gist of Idea
Empiricism explores necessities and concept-limits by imagining negations of truths
Source
Alan Sidelle (Necessity, Essence and Individuation [1989], Ch.1)
Book Reference
Sidelle,Alan: 'Necessity, Essence and Individuation' [Cornell 1989], p.12