 One way to answer the question about the nature of a priori justification and knowledge is to adopt a bottom up approach. Start with contrasting examples like the fifteen above and construct a theory that explains the difference. Timothy Williamson objects to this approach on the grounds that it may result “in a distinction of no special significance like a taxonomy of plants and animals based on color” or the classification of plants into bushes and non-bushes (2013: 291 and 309). Ultimately, that is what he argues: the difference between a priori and a posteriori knowledge is insignificant.