Contradictory Premises. Conclusions are drawn from the interactions of premises: where two premises contradict each other, there can be no interaction and hence no conclusion. Similarly, if the definitions of two terms conflict with or exclude each other, then those two terms cannot be simultaneously ascribed to a single object or event. The classic example of contradictory premises is the question, "What will happen if an irresistible force meets an immovable object?" The problem here is that in a universe where an irresistible force has been defined to exist, there cannot also exist an immovable object, because then the force would not be irresistible. Conversely, if there is discovered or defined such an item as an immovable object, then
by definition there can be no such thing as an irresistible force.
This fallacy's most popular appearance is in the form of a challenging question, because questions with contradictory premises are such brain teasers. In each case, though, no answer can be given because the premises cannot both be true.
- Into what shape of hole would a round square fit?
- If an object is all black and all white at the same time, what color is it?
- If an object is both stationary and traveling at an infinite rate of speed, how long will it take to meet itself?
- If God can do anything, can he make a stone so heavy that he cannot lift it?
- If God is all powerful, can he put himself out of existence and come back with twice the power he had before?