I once saw this posted somewhere but forgot, so I'll now proceed to make it up 20% from memory 80% from scratch
Valid ways to prove something the scientific way:
Proof by confusion: "If y is x then c is a but if b ate c then d would still be the quantum inheritor of x, which my data shows, is t without the w element. Therefore, P is true."
Proof by violence: "P is true. If anyone has any objections, I'll shoot you."
Proof by matter-of-fact: "P is true. Anyone who can't see it should go back to elementary school."
Proof by blatant denial: "... therefore P is true." "But professor, in step 16 of your proof, the y should be negative, not positive." :: stealthily wipes the blackboard clean :: "y? What y? Where do you see a y? You need glasses, boy."
Proof by Circular Logic: "If P is false then X would be true. If X were true, Y would be false. if Y were false, P would be false. Therefore, P is true."
Proof by Complex Terminology: "The eco-semiplatetectonic movement of the unilateral-quantum-mechanical value is zero. Therefore, P is true."
Proof by Abstraction: "The summer swans are basking in the sunlight of our morality. Therefore, P is true."
All I can think of right now