To prove: nothing causes itself (where by "cause" here we mean "is the efficient cause of")
Assume: | 1. | Something does cause itself. |
Call one such thing "A." | ||
So the assumption is: A causes A. | ||
Premise: | 2. | If x causes y, then x is prior to y. |
So: | 3. | A is prior to A. (1,2) |
Premise: | 4. | Nothing is prior to itself. |
So: | 5. | A is not prior to A. (4) |
So: | 6. | Contradiction! (3, 5) |
So: | 7. | The assumption is false. (1-6, reductio) |
I.e., Nothing causes itself. |