I advance a novel argument for an infallibilist theory of knowledge, according to which we know all and only those propositions that are certain for us. I argue that this theory lets us reconcile major extant theories of knowledge, in the following sense: for any of these theories, if we require that its central condition (evidential support, reliability, safety, etc.) obtains to a maximal degree, we get a theory of knowledge extensionally equivalent to infallibilism. As such, the infallibilist can affirm (...) that, when their conditions are suitably interpreted, most post-Gettier theories of knowledge offer necessary and sufficient conditions for knowledge. The infallibilist can thus reconcile major theories of knowledge, and is in a better position to explain the intuitive appeal of these theories than the fallibilist who only accepts one of them, and rejects the rest. (shrink)