This paper uses a formal analysis of the relation of ‘parity’ to make sense of a well-known solution to Parfit’s ‘mere addition paradox’. This solution is sometimes dismissed as a recourse to ‘incomparability’. In this analysis, however, the solution is consistent with comparability, as well as transitivity of ‘better than’. The analysis is related to Blackorby, Bossert and Donaldson’s ‘incomplete critical-level generalised utilitarianism’ (ICLGU). ICLGU is inspired by Parfit’s work and can be related to the analysis of parity, though the distinctive ‘mark’ of parity suggests that the boundaries of a set of critical levels is not exact. One has to allow for vagueness to make an account based on parity plausible. These accounts are then contrasted with Broome’s view which also involves vagueness.