Most logic-based AI research works at a meta-theoretical level, producing new logics and studying their properties. Little effort is made to show how these logics can be used to formalise object-level theories of common sense. In the spirit of Pat Hayes's Naive Physics Manifesto, the present paper supplies a formalisation of a non-trivial benchmark problem in common sense physical reasoning, namely how to crack an egg. The formalisation is based on the event calculus, a well-known formalism for reasoning about action. Along the way, a number of methodological issues are raised, such as the question of how the symbols deployed in the formalisation might be grounded through a robot's interaction with the world. 2003 Published by Elsevier B.V.