他的古怪行为一定事出有因。

There has to be a reason for his strange behaviour.

生命的意义是什么？是否一切事出有因？为何苦难会降临到世间？

What's the meaning of life? Does everything happen for a reason? Why is there suffering in the world?

纵算相信事出有因，我始终还有无法明了的一件事，即疾病——颠覆人类生存的宿命。

However, the thing that I've never understood is illness; this is a fate which opposes our own existence.