The early history of philosophical thought experiments remains largely unwritten. In this article I argue for the importance of Ibn Sina (the Latin Avicenna, 980-1037) for understanding the gradual systematization of Aristotelian thought experiments and their methodology. Through a close examination of Avicenna's novel take on Aristotle's refutation of self-motion, I develop a case for Ibn Sina being possibly the first Peripatetic to have a reflected view of what thought experiments are and how they function. Important here is Ibn Sina's theory of the inner senses, especially his distinction between the faculties of imagination and estimation, which allows Ibn Sina to set apart idealized abstractions from imaginative feats. Ibn Sina's case demonstrates how in the Aristotelian tradition, a naturalized basis can be postulated that will underwrite the dependability of (properly conducted) philosophical thought experiments, something to which more modern thinkers no longer have access.
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