  Contingency and accident are two important notions in philosophy and
philosophical logic. Their meanings are so close that they are mixed sometimes,
in both everyday discourse and academic research. This indicates that it is
necessary to study them in a unified framework. However, there has been no
logical research on them together. In this paper, we propose a language of a
bimodal logic with these two concepts, investigate its model-theoretical
properties such as expressivity and frame definability. We axiomatize this
logic over various classes of frames, whose completeness proofs are shown with
the help of a crucial schema. The interactions between contingency and accident
can sharpen our understanding of both notions. Then we extend the logic to a
dynamic case: public announcements. By finding the required reduction axioms,
we obtain a complete axiomatization, which gives us a good application to Moore
sentences.
