Two questions are distinguished: how to program a machine so that it behaves in a manner that would lead us to ascribe consciousness to it; and what is involved in saying that something is conscious. The distinction can be seen in cases where anaesthetics have failed to work on patients temporarily paralysed. Homeostatic behaviour is often cited as a criterion for consciousness, but is not itself sufficient. As the present difficulties in surmounting the `frame problem' show, ability to size up situations holistically is more important; so is the explanatory role of the concept. Consciousness confers evidential status: if we ascribed consciousness to an artefact, we should be prepared to believe it, when it said its RAM was hurting, even though we could detect nothing wrong, contrary to our thinking of it as an artefact. A further difficulty arises from self-awareness and reflexivity.