Which is prior, the whole or its parts? The monist holds that the whole is prior to its parts, and thus views the cosmos as fundamental, with metaphysical explanation dangling downward from the One. The pluralist holds that the parts are prior to their whole, and thus tends to consider particles fundamental, with metaphysical explanation snaking upward from the many. There seem to be physical and modal considerations that favor the monistic view. Physically, there is good evidence that the cosmos forms an entangled system and good reason to treat entangled systems as irreducible wholes. Modally, mereology allows for the possibility of atomless gunk, with no ultimate parts for the pluralist to invoke as the ground of being.