Can all the philosophical disciplines verify their own answers? What about the social disciplines? Do you just ignore questions which aren't cleanly reducible to science or mathematics?
Consider:
http://en.wikipedia.org/wiki/Critical_thinking
It doesn't even mention the scientific method!
http://en.wikipedia.org/wiki/Scientific_method
The revolution in the human condition has been brought about by application of the scientific method - it's the most useful critical thinking skill ever devised.