 The essentialist thesis is often stylized by writing “water = H2O” or “(all and only) water is H2O”. Ignoring the issue of whether the identity makes sense (Needham 2000) and of understanding what the predicates apply to in the second formulation (Needham 2010a), it is not clear that either formulation expresses the kind of thesis that essentialists intend. “H2O” is not a description of any microstructure. Rather, “H2O” is a compositional formula, describing the combining proportions of hydrogen and oxygen to make water.