What, If Anything, Can You Know for Certain?

One of the traditional goals of epistemology—the branch of philosophy that concerns theories of knowledge—is to identify beliefs that are certain, beyond any doubt. This pursuit is the major preoccupation of the famous philosopher, Descartes, who was not satisfied with Plato’s theory.  Plato believed that only human reasoning could lead to genuine knowledge, beliefs that can be held with certitude.   For Plato, of course, these supposedly indubitable beliefs concern the Forms—a metaphysical theory that many subsequent philosophers have rejected. 

Accordingly, the question for you is:  what, if anything, do you know with absolute certainty?  On what basis can you justify this conviction?  How might a sceptic challenge your belief?