 A common objection to even restricted infallibility claims is the idea, often attributed to Wittgenstein, that where one cannot be wrong, one cannot be right either. For instance, Wright maintains that the possibility of error is required for concept application, which is in turn required for substantial self-knowledge.“[E]rror—if only second-order error—has to be possible, if a genuine exercise of concepts is involved” (Wright 1989: 634).