  Topos theory has been suggested by Doring and Isham as an alternative
mathematical structure with which to formulate physical theories. In particular
it has been used to reformulate standard quantum mechanics in such a way that a
novel type of logic is used to represent propositions. In this paper we extend
this formulation to include temporally-ordered collections of propositions as
opposed to single-time propositions. That is to say, we have developed a
quantum history formalism in the language of topos theory where truth values
can be assigned to temporal propositions. We analyse the extent to which such
truth values can be derived from the truth values of the constituent,
single-time propositions.
