Philosophical interest in thought experiments has grown over the last couple of decades. Several positions have emerged, defined largely by their differing responses to a perceived epistemological challenge: how do thought experiments yield justified belief revision, even in science, when they provide no new empirical data? Attitudes towards this supposed explanandum differ. Many philosophers accept that it poses a genuine puzzle and hence seek to provide a substantive explanation. Others reject or deflate the epistemic claims made for thought experiments.In this (...) paper I present a model for many thought experiments in philosophy and science. The model doesn't assume that thought experiments in fact manage to achieve epistemic justifi cation, but it allows us to see how they aspire to do so. It also emphasises both the parallels and the discrepancies between thought experiments and ordinary scientific experiments. (shrink)