However, (2) does not capture the force of (1) either, since ravens that are non-black because of the environmental conditions they experience, rather than the genetic endowment they are born with, would falsify (2) without intuitively leading us to reject (1). And it seems as if, for any way of adding more qualifications to the unless-clause, we can come up with more mere exceptions we have not yet captured. Let’s call such an unless-clause open-ended, and let’s call the cp-generalization that gives rise to such an unless-clause open-ended, as well. Of course, there are some ways of listing the exceptions that does not result in an open-ended unless-clause. We could say that ravens are black unless they are abnormal. By itself, this does not represent any advance beyond (1). But if we do not help ourselves to these expressions, the list of merely apparent exceptions is open-ended.0
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