  Frank Jackson (1982) replies to this objection by saying that it is the brain state associated with pain that evolves for this reason: the sensation is a by-product. Evolution is full of useless or even harmful by-products. For example, polar bears have evolved thick coats to keep them warm, even though this has the damaging side effect that they are heavy to carry. Jackson’s point is true in general, but does not seem to apply very happily to the case of mind. The heaviness of the polar bear’s coat follows directly from those properties and laws which make it warm: one could not, in any simple way, have one without the other. But with mental states, dualistically conceived, the situation is quite the opposite. The laws of physical nature which, the mechanist says, make brain states cause behaviour, in no way explain why brain states should give rise to conscious ones. The laws linking mind and brain are what Feigl (1958) calls nomological danglers, that is, brute facts added onto the body of integrated physical law. Why there should have been by-products of that kind seems to have no evolutionary explanation.