Principle of nonvacuous contrast

The principle of nonvacuous contrast is a logical or methodological principle which requires that a genuine predicate never refer to everything, or to nothing, within its universe of discourse.

References

*cite book |author=William Dray |year=1964 |title=Philosophy of History |publisher=Englewood Cliffs, NJ: Prentice-Hall, Inc. |pages=29 pp