Bias seems to be everywhere. Biased media outlets decisively influence the political opinions and votes of millions of people. Discriminatory policies favor some racial groups over others. We tend to judge ourselves more favorably than our peers, and more favorably than the evidence warrants. But what is it, exactly, for a person or thing to be biased?In Bias: A Philosophical Study, Thomas Kelly explores a number of foundational questions about the nature of bias and our practices of attributing it. He develops a general framework for thinking about bias, the norm theoretic account, and shows how that framework illuminates much that we say and think about bias in both everyday life and the sciences. He argues provocatively that both morality and rationality sometimes require us to be biased; that groups of people can be biased evenif none of their members are; that we are often rationally required to believe that those who disagree with us are biased, even if we know absolutely nothing