Rationality (or something similar) is usually given as the relevant difference between all humans and animals; the reason humans do but animals do not deserve moral consideration. But according to the Argument from Marginal Cases not all humans are rational, yet if such (marginal) humans are morally considerable despite lacking rationality it would be arbitrary to deny animals with similar capacities a similar level of moral consideration. The slippery slope objection has it that although marginal humans are not strictly speaking (...) morally considerable, we should give them moral consideration because if we do not we will slide down a slippery slope where we end up by not giving normal humans due consideration. I argue that this objection fails to show that marginal humans have the kind of direct moral status proponents of the slippery slope argument have in mind. (shrink)