The mulitiple realizability thesis has been a cornerstone of anti-reductivist arguments across several areas of philosophy, including philosophy of mind and cognitive science, philosophy of artificial intelligence, and in the metaphysics of science. Yet, despite the signficance and widespread philosophical import of this thesis, there continues to be debate around its content, plausibility, and implications. What exactly does multiple realizability thesis maintain? What does the thesis entail? And what should count as evidence in favor of multiple realizability (in different domains)? To explore these questions, this seminar will proceed chronologically, looking at the historical development of the philosophical ideas and debates surrounding the multiple realizability thesis, how the thesis itself has evolved, and the impact it has had in both philosophy and the sciences.