Two seventeeth-century Scottish Catholic philosophers, Robert Balfour and William Chalmers, are introduced and their accounts of the metaphysics of the Eucharist are discussed. Their ideas are largely in terms of the Aristotelian concepts of substance, accident and inherence, with special attention paid to the idea that the essence of an accident is not its actual inherence (that is, its act of inhering) in a substance but its aptness for inherence in a substance. Balfour appears to accept this (Thomist) doctrine. But (...) Chalmers has a different story to tell. He holds that the essence of an accident is not its actual inherence or its power to inhere (which includes its aptness for inherence), but instead belongs to what he terms the ‘root and basis’ of that power. I speculate briefly about a possible Scotistic interpretation of his words. (shrink)