ABSTRACT
The existence of a special class of thought experiments-platonicwas asserted earlier when the taxonomy was created. This chapter is an attempt to vindicate that claim. I shall go about this by arguing, first, that these thought experiments are indeed a priori; and second, that laws of nature are relations between independently existing abstract entities. The existence of such entities gives the thought experimenter something to perceive. It also makes obvious which sense of a priori is at work; it is the same as that involved in mathematical platonism. Neither linguistic conventions nor Kantian forms of perception-both candidate accounts of the a priori-are involved. Some laws of nature, on my view, can be seen in the same way as some mathematical objects can be seen. Of course, no case for any theory can be made except in comparison with alternative accounts; scattered throughout this chapter (as in the last) are remarks on the rival views of Kuhn, Mach, and Norton.
