It is suggested that one way of understanding contexts is to view them as sets of topics. Accordingly, a description of a given context would be a set of sentences about the set of topics concerned. The paper presents a model-theoretic and axiomatic characterisation of a logic for sentences of the type: " sentence 'p' is about topic t', and then discusses some features of that logic. The model-theory makes particular use of the three valued semantics of Bochvar. Finally, some remarks are made about application domains in which it would be useful to have a logic for reasoning about topics.