Tamar Szabo Gendler 
Thought Experiment [PDF ebook] 
On the Powers and Limits of Imaginary Cases

This book offers a novel analysis of the widely-used but ill-understood technique of thought experiment. The author argues that the powers and limits of this methodology can be traced to the fact that when the contemplation of an imaginary scenario brings us to new knowledge, it does so by forcing us to make sense of exceptional cases.