For a premodern scientist, matter is what made an apple this apple and also distinguished that apple from the mental idea. Matter was the carrier of three-dimensional extension and the bearer of forms, which in turn articulated the patterns of definition, shape, and intrinsic nature of this or any apple. Premodern knowing depended on form whence matter appears to inevitably escape it – as matter is, by definition, what is other than form. How was the premodern understanding of corporeality shaped by the grounding and yet shadowy functions by matter? And how could premodern thinkers grasp what matter is – and subsequently how it can properly satisfy the physical conditions of dimensionality and corporeality – if matter cannot be known? This paper will examine two alternative strategies that were put in place to resolve this puzzle in the High Middle Ages: the denial that knowing matter is possible (Aquinas) and the assumption that it can be known albeit feebly and mediatedly (Scotus and Ockham). While both strategies meant to resolve this puzzle, they also contributed to stress the theoretical flaws which originated by the tension between the physical functions of matter and its (un)knowability. This crucial impasse would facilitate the identification of matter and materiality, as it required philosophers and scientists to provide new answers and narratives beyond the Aristotelian tradition and to drastically contribute to the final ousting of Aristotelian metaphysics from natural science.
