Ed thinks that the assumption that the domain of quantification is a domain of existing individuals is a contingent assumption. But I didn't say that, and it is not. It is a necessary assumption if (1) [namely that ‘Island volcanos exist’ is logically equivalent to ‘Some volcano is an island.’] and sentences of the same form are to hold. [My emphasis]But he then says that there is nothing in the nature of logic to stop us from quantifying over nonexistent individuals, which I don't follow at all. We start with the initial logical or definition assumption about the meaning of the verb 'exists'.
(1) 'A golden mountain exists' = 'Some mountain is golden'
If we accept that, we also have to accept the equivalence where the right hand side does not explicitly contain the copula 'is', but has a verb which is logically equivalent to a copula plus participle. That is a standard assumption, namely that 'John runs' is logically equivalent to 'John is running'. Thus
(2a) 'John owns a house' = 'some house is owned by John
and thus, given (1), and given that John owns a house, it follows that:
(2b) John's house exists
A brief qualification here. The equivalence in (2a) only holds when the verb is what I call 'logically transitive. I explain this idea here. Clearly, if John wants a beautiful wife, it does not follow that some beautiful wife is wanted by John. Given that, it is plain that our Brentano equivalence applies to the following quantifier type sentences:
(3) 'The domain contains islands' = 'some individuals in the domain are islands' = 'there exist individuals in the domain which are islands'
(4) 'The term 'volcano' ranges over volcanos' = 'ranged-over volcanos exist'
and so on. Hence there clearly is something 'in the nature of logic' which prevents us quantifying over non-existent individuals, namely the same thing as what prevents us owning non-existent houses, given the definition of 'exists' above. I can't believe that Bill does not grasp this. I think what he fails to see is that 'logical' verb phrases like 'ranges over', 'contains', 'quantifies over' are subject to the same logical rules as 'owns', 'lives next door to', 'loves' and so on. That any domain contains existing individuals is therefore a logical truth.