When we observe external objects, we observe their structure and function; that’s all. Such observations give no reason to postulate any new class of properties, except insofar as they explain structure and function; so there can be no analogue of a ‘hard problem’ here. Even if further properties of these objects existed, we could have no access to them, as our external access is physically mediated: such properties would lie on the other side of an unbridgeable epistemic divide. Consciousness uniquely escapes these arguments by lying at the centre of our epistemic universe, rather than at a distance. In this case alone, we can have access to something other than structure and function.

David Chalmers, ‘Moving forward on the Problem of Consciousness’, Journal of Consciousness Studies, vol. 4, no. 1 (1997), p. 6