In this paper, I argue for 'perfect' as a type of aspectual semantics which can have multiple instantiations. I also challenge the claim in Iatridou et al. (2001) that the interval between event time and reference time does not have "a distinguished status" in the perfect. I argue that not only do languages pay attention to this interval, but that some, including Scottish Gaelic (Gaelic), grammaticalize information about it. I provide an analysis of perfect in Gaelic as a second type of grammatical aspect (in the spirit of Smith (1997), Iatridou et al. (2001), and Pancheva & von Stechow (2004)). I consider three aspectual particles in the language: I analyze air as an unrestricted retrospective perfect particle; as dèidh as a restricted retrospective perfect particle; and gu as a restricted prospective perfect particle. The data I present indicate that a complete characterization of the perfect (at least in Gaelic) should include both retrospective and prospective semantics, as well as a consideration of the event time-reference time interval.