If you judge me to be conscious because of my behaviour, then you must judge as conscious any entity that shows similar behaviour - you cannot have it both ways and stick to some 'essentialist' idea of humanity

This is the only post that addresses the point. I don't agree with your criteria for defining machine, but I won't take it up with you.

Since it is the only point with real relavance to language itself, I will add that the notion of consciousness is suspect for the very reason you assert observed behavior as the sole criterion for imputing it. As something utterly private, consciousness is not something around which there can be an evolved language. If the concept lies outside the horizon of language, both the term and its assertion are meaningless. This may spur controversy best avoided (I've learned my lesson). Suffice it to say, an analysis of certain forms of speech reveals an inadequacy of the term to its purported meaning:* we think we mean things which cannot be meant. That takes it a step past shank's point, but without changing direction.

IP

*[I-realize-I've-set-myself-up-for-a-dig emoticon]