What is a proof?

[Kayenneh]

All men are mortal. (premise)
Socrates was a man. (premise)
Socrates was mortal. (conclusion)

This only works if you have all the parameters. One another classic example is this:

a) Swans are white birds.
b) Billy is a swan.
c) Therefore Billy is white.

If I tell you that Billy is actually black, you might disagree, since you've just deduced (based upon your experience that all swans you've seen are white) that I'm wrong. But then I show you this picture of Billy:



and prove to you that your deduction is faulty and Billy is indeed a black swan. Then you must change your assumptions to:

a) Swans are either black or white.
b) Billy is a swan.
c) Therefore Billy is black or white.