He wrote under psuedonyms because he said there is no way to define human existence which can avoid contradictions. He worked in nice ways. Kierkegaard was a Christian existentialist. Well, you might say he was a subjective believer rather than a Christian. He says that if you are sure about your faith for even one second, you have lost it.
Faith is always at risk.
You cannot KNOW what you have faith about. The constant inward striving is what makes faith, the trust in the absurd. He said that true Christianity cannot be known and looked at as science can. He said that crowds make the untruth. When we are in a crowd, we are no longer ourselves, but rather, part of a whole.