 Not every way of describing a belief-forming process carves psychological reality at its joints. Consider, for example, the process type, forming a perceptual belief while wearing green socks. Intuitively, this is an “inappropriate” or “irrelevant” way of describing Smith’s belief-forming process. But why is it inappropriate? According to psychological approaches, it is inappropriate because it mentions features of Smith’s circumstances that play no causal role in the psychological processes responsible for his belief.