Abstract
The paper investigates the senses in which the world may be thought external, and argues that none of them supports doubt about the possibility of knowledge of the world. Scepticism sometimes depends on certain erroneous conceptions of perception, especially those which lead to belief in 'inner, representational states'. How we perceive things depends on the satisfaction of certain general conditions--on what concepts we have, on the kind of senses we have, and so on a kind of anthropocentricity; but this does not prevent objectivity, even in the case of secondary qualities