“Tom Mitchell, a leading symbolist, calls it “the futility of bias-free learning.” In ordinary life, bias is a pejorative word: preconceived notions are bad. But in machine learning, preconceived notions are indispensable; you can’t learn without them. In fact, preconceived notions are also indispensable to human cognition, but they’re hardwired into the brain, and we take them for granted. It’s biases over and beyond those that are questionable.”