Whenever I am like this, too critical of the ideas of others and too sure of my own I must remind myself there are only two things that I really know--one: that I exist. I could say I live and am a human being but those things are also matters of definition so I can't be sure. Two: That I know nothing except these two things. One might say that this is being silly and extreme but I think it is best to start out with as few as possible things which you hold to be unquestionably true and start from there.