But there is one advantage, which can be made both comprehensible and interesting to even the dullest and most reluctant student of such transcendental investigation, namely this: That the understanding occupied merely with its empirical use, which does not reflect on the sources of its own cognition, may get along very well, but cannot accomplish one thing, namely, determining for itself the boundaries of its use and knowing what may lie within and what without its whole sphere; for to this end the deep inquiries that we have undertaken are requisite.