The decomposition of ∆E int in Eq. ( ) is not unique, insofar as there is no quantum-mechanical operator that represents dispersion (or polarization, etc.). As a result of this ambiguity, a variety of EDA schemes have been suggested for use with DFT, and there are a few EDAs for correlated wavefunction methods as well. However, there is also no shortage of criticism over the fundamentally ill-defined nature of such analyses, with some going so far as to suggest that for "weak" interactions ( 5 kcal/mol), we should not even bother. We agree with the general sentiment that EDAs are often over-interpreted ("how many kJ/mol can dance on the head of a pin?"), 1 but a 5 kcal/mol threshold for giving up feels too conservative. The energy of the single hydrogen bond in (H 2 O) 2 is 3.2 kcal/mol, and we should demand that a useful EDA can discern a hydrogen bond from some other type of intermolecular interaction.