I once read, in the preface to a book of mathematics, that everything can be proved except a few basics which everybody knows to be true anyway. I think the example they gave was 2 x 2 ALWAYS equals 4. The author then went on to say that they overcame that problem by getting a large body of mathematicians to agree that it was so, and by calling everybody who disagreed, mad.
Normal is fitting in with the majority of society, or of a group.
Or is it?
Normal for an atheist is to think that all Christians are mad. Normal for a Christian is to pity atheists and think they're all crazy. Normal for an American is to work hard. It's nuts to miss an opportunity. Normal for an Australian is sport and recreation. Working long hours is barmy.