How do I know...

You are a Skeptic?

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Robert Kurzban shows us that the key to understanding our behavioral inconsistencies lies in understanding the mind's design. The human mind consists of many specialized units designed by the process of evolution by natural selection. While these modules sometimes work together seamlessly, they don't always, resulting in impossibly contradictory beliefs, vacillations between patience and impulsiveness, violations of our supposed moral principles, and overinflated views of ourselves.

This modular, evolutionary psychological view of the mind undermines deeply held intuitions about ourselves, as well as a range of scientific theories that require a "self" with consistent beliefs and preferences. Modularity suggests that there is no "I." Instead, each of us is a contentious "we"--a collection of discrete but interacting systems whose constant conflicts shape our interactions with one another and our experience of the world.

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http://press.princeton.edu/titles/9271.html