When you are born you become a member of a collective agreement we call humanity, this is a collective agreement between billions of smaller individuals. Personal egos which come together to create a family, a community, a society, a nation, and finally an agreement called humanity.

Rationality is the quality or state of being rational, a state based on our agreeability to reason. Rationality implies the conformity of one's beliefs with one's reasons to believe, but really what we called rationality is our ability to recognition patterns, an unconscious state where the brain identifies patterns that it can use to predict and expect what is coming.