| I think that Jeremy has covered the most logical and reasonable answers in this thread. Jeremy, you're obviously a man of impressive intellect and knowledge. The only things that I think I might add is that, although implied, a Theory of Mind has not been directly addressed. Also, there is an issue of semantics here.
Semantics first--In addition to the problem of difficulties of meaning and transltion between languages, there is often an important difference in the meaning and use of many terms between common, laymens language and the meaning and technical use of these terms within the discipline of a particular field--in this case biology--particularly here, the biology of lower invertebrate animals. I rather think that in his original post, Anthony is thinking of and referring to the term "irritation" in it's common usage which refers most directly to human experience. In the area of biology I believe that, as Jeremy has explained so well, it has a more functional definition that cannot be equated with its' common, human-referenced usage.
Although there is no concensus in psychology on the definition of the term "mind," it generally is accepted that there is such a thing on the basis that one will know a mind when one sees it. Part of the probable definition of mind is generally accepted, I believe, that a mind is dependant on a certain complexity and organization of a brain. Although at what point a brain produces a mind is very debatable, it is generally considered to be far above that of molluscs, a type of creature that, to my knowledge doesn't even have a brain. At such a low level of complexity, it seems that such human terms as "enjoy," "dislike," happy," "like," etc. have no meaning and only functional definitions such as described by Jeremy above have any real use or meaning. My point would be the answer to this question: How can a creature experience pain, discomfort, sadness or any of these human-referenced states if it has no mind to experience and interpret them?
Marc  |