No one is rational

Some time ago I read a piece of text in a book that really got to me. This text is extracted from the book"Children of the mind", the fourth book in Ender's saga, by Orson Scott Card. Let each of you draw what you will.

"No one is rational - Said Miro -. We all act because we are convinced of what we want, and we believe tha through our actions we will attain it. But we never know anything with absolute certainty, so all our rationale are just inventions to justify what we wer going to do anyway before we thought up any reasons."