  This paper investigates quantum logic from the perspective of categorical
logic, and starts from minimal assumptions, namely the existence of
involutions/daggers and kernels. The resulting structures turn out to (1)
encompass many examples of interest, such as categories of relations, partial
injections, Hilbert spaces (also modulo phase), and Boolean algebras, and (2)
have interesting categorical/logical properties, in terms of kernel fibrations,
such as existence of pullbacks, factorisation, and orthomodularity. For
instance, the Sasaki hook and and-then connectives are obtained, as adjoints,
via the existential-pullback adjunction between fibres.
