I point out a simple algebraic error in Joy Christian’s refutation of Bell’s theorem. In substituting the result of multiplying some derived bivectors with one another by consultation of their multiplication table, he confuses the generic vectors which he used to define the table, with other specific vectors having a special role in the paper, which had been introduced earlier. The result shoul...

We argue that the detection and refutation of non-theorems, and the discovery of appropriate counterexamples, is of vital importance to the Grand Challenge of a Program Verifier.