 In reply to this sort of response, critics of intuition-based views of a priori justification have said that at least different types of perception can be checked against each other, say, vision against touch (Weatherson 2003: 4). The critics of intuition add that while we can distinguish circumstances where, say, vision is unreliable from circumstance where it is not, nothing similar can be done when it is a matter of intuitions. For instance, we can distinguish conditions where the lighting conditions, or the person’s eyesight, are bad from ones where they are not. We can know whether we are in a desert where optical illusions occur and whether we are not. At least sometimes we can tell whether we are hallucinating or not.