The human stomach was said to be one of God’s greatest inventions, an oven for his earthly chemistry lab. The human ability to understand and manipulate individual chemical elements would always pale in comparison to the alchemy of digestion, which was designed with celestial complexity. In this model, digestion takes on expansive metaphysical dimensions that appear far removed from how we might conceive of digestion today. But digestion theories are fundamental representations of how one conceives of the threshold where the body meets the world. As such, any understanding of how the body digests is always in some way metaphysical, a product of models for how the body is more broadly situated in the world within a given cosmology.