 A standard answer to the question about the difference between a priori and empirical justification is that a priori justification is independent of experience and empirical justification is not, and this seems to explain the contrasts present in the fifteen examples above. But various things have been meant by “experience”. On a narrow account, “experience” refers to sense experience, that is, to experiences that come from the use of our five senses: sight, touch, hearing, smell, and taste. However, this narrow account implies that justification based on introspection, proprioception (our kinesthetic sense of the position and movements of our body), memory, and testimony are kinds of a priori justification. And if we had different senses, like those of bats (echolocation) and duck-billed platypuses (electrolocation), experiences based on those senses would provide a priori, not empirical, justification on this account which takes a priori justification to be independent of experiences based on the senses we have.