As noted earlier, it is probably impossible to firmly logically prove there is no Bigfoot, in the same way as Russell's Teapot. However, and this come from the Mathematician in me, there are a few strategies you can try to either disprove or weaken a claim.

##Proof by Contradiction## Basically, assume that the claim is true, and show that it being true causes some logical impossibility. This is more or less the only way to actually prove something false. Things to help support this kind of argument:

• Include requirements. I.E If Bigfoot is 8 feet tall and a mammal, then his heart has to be some size, food intake this, skeletal structure that...
• Include other, given truths. I.E If we assume Bigfoot exists and the Sun is hot, then ..{argument}.. which is a contradiction.
• Take an extreme. I.E if Bigfoots exists, there must be a smallest Bigfoot..
• Generalize. I.E If Bigfoot exists, then at least one undocumented mammal exists...

##Proof by Contrapositive## A => B implies not B => not A.

This one is weird, and probably not applicably outside of rigidly defined areas like math. But essentially, you take the contrapositive and prove it must be true. In a single statement case this is redundant, and becomes proving "Bigfoot does not exist", which is where we started. But apply it to a specific implication used, and it can be useful. I.E "Most photographs are not fake => Bigfoot exists" would also imply "If BigFoot does not exist => Most photographs are fake" which is just a silly implication.

I know the example for this one is weak, I'm trying to come up with a better one, but these cases are usually relatively subtle and require a lot of context

##Probabilistic Proof## Instead of absolutely proving a claim wrong, you can prove that a claim is not likely to be true, therefore the inverse is more likely to be true, therefore the claim is more likely to be false than not. Not an absolute proof, but certainly weakens a claim if it's most likely to be false. Tips:

• Look at implications. Bigfoot existing need X acres of land never surveyed, there have been Y acres surveyed out of Z, so Bigfoot's X being within those Y acres is only ~Y/Z*X
• Look for correlations. I.E Number of recorded sightings of Bigfoot decreased in proportion to availability of cameras, a regression or even common sense says that's very unlikely if Bigfoot exists.

As noted earlier, it is probably impossible to firmly logically prove there is no Bigfoot, in the same way as Russell's Teapot. However, and this come from the Mathematician in me, there are a few strategies you can try to either disprove or weaken a claim.

Proof by Contradiction

Basically, assume that the claim is true, and show that it being true causes some logical impossibility. This is more or less the only way to actually prove something false. Things to help support this kind of argument:

• Include requirements. I.E If Bigfoot is 8 feet tall and a mammal, then his heart has to be some size, food intake this, skeletal structure that...
• Include other, given truths. I.E If we assume Bigfoot exists and the Sun is hot, then ..{argument}.. which is a contradiction.
• Take an extreme. I.E if Bigfoots exists, there must be a smallest Bigfoot..
• Generalize. I.E If Bigfoot exists, then at least one undocumented mammal exists...

Proof by Contrapositive

A => B implies not B => not A.

This one is weird, and probably not applicably outside of rigidly defined areas like math. But essentially, you take the contrapositive and prove it must be true. In a single statement case this is redundant, and becomes proving "Bigfoot does not exist", which is where we started. But apply it to a specific implication used, and it can be useful. I.E "Most photographs are not fake => Bigfoot exists" would also imply "If BigFoot does not exist => Most photographs are fake" which is just a silly implication.

I know the example for this one is weak, I'm trying to come up with a better one, but these cases are usually relatively subtle and require a lot of context

Probabilistic Proof

Instead of absolutely proving a claim wrong, you can prove that a claim is not likely to be true, therefore the inverse is more likely to be true, therefore the claim is more likely to be false than not. Not an absolute proof, but certainly weakens a claim if it's most likely to be false. Tips:

• Look at implications. Bigfoot existing need X acres of land never surveyed, there have been Y acres surveyed out of Z, so Bigfoot's X being within those Y acres is only ~Y/Z*X
• Look for correlations. I.E Number of recorded sightings of Bigfoot decreased in proportion to availability of cameras, a regression or even common sense says that's very unlikely if Bigfoot exists.