Philosophical scepticism (US spelling skepticism) is a systematic philosophy that questions the notion that absolutely certain knowledge is possible. A philosophical sceptic does not claim that truth is impossible (which itself would be a truth claim), instead it recommends “suspending belief” since generally they agree that knowledge requires justification. Scepticism can be classified according to its scope. Local scepticism involves being sceptical about particular areas of knowledge, e.g. moral scepticism, scepticism about the external world, or scepticism about other minds, whereas global scepticism is sceptical about the possibility of any knowledge at all. Empiricism is a closely related, but not identical, philosophy to philosophical scepticism. Empiricists claim empiricism is a pragmatic compromise between philosophical scepticism and general science. Philosophical scepticism is in turn sometimes referred to as “radical empiricism“.