The master argument of Diodorus Cronus (fl. c.3rd c. bc) seems designed to show that nothing is possible which neither is nor will be true. It proceeded by finding an inconsistency between three propositions: everything that is past is necessary, the impossible does not follow from the possible, what neither is nor will be is possible. If these are inconsistent, and the first two are true, then the conclusion follows, but modern modal logic does not sustain the argument. Berkeley's argument that it is impossible to have an idea of a tree of which nobody is conscious (for your having the idea of it makes it true that someone is conscious of it) is also referred to as his master argument.