In maths it is always true that 2+2=4
Not true.

2+2=8 mod 4
Yes, you can use that argument (and to use the example that 'two plus two always equals four' is too simplistic- but i was reading 1984 the other day so that quote was stuck in my head), but the fact still remains that to get any answer you still have to use a set pattern, and you can use a set pattern to find any answer to any maths question. Humanities subjects are different in that there is no set pattern to follow. You make it up as you go allong and explore ranges of answers, from what is right to what is semi-right and to what is probably wrong.
Theoreticly, if you understood and knew every pattern and every rule governing every area of every field of mathmatics, you could answer any question wich was maths based. However, no matter how much you know about an arts subject, there is always a way of finding a different answer. Effectivley, I propose that whilst the number or rules which govern maths is finite, the number of rules which govern art are infinite.
Yes, you can ask what i base this on, and the only thing that i can base it on is that maths is logic based, whilst art is not logic based.
EDIT: you know, I'm gonna stop digging a hole for myself. You're right, maths is prety good.