It seems that logicians are of differing opinions regarding the existential import of propositions. The "modern" view holds that universal propostions (All X is Y) do NOT assert the existence of their subjects but that particular propositions (Some X is Y) do.
I'm confused about this. It seems to me that in neither case can you assume anything; i.e.: sometimes you can and sometimes you can't assume that a subject "exists". In your book "Future Logic" you don't go into this (at least, I haven't been able to find any view one way or the other), so is this essentially a non-issue for you? and if so, why?
This topic is dealt with in Future Logic in Chapter 41, under the heading of Modalities of Subsumption.
The existential import theory is rather limited because it only distinguishes between actual being and non-being, whereas in fact the way we use terms in practice is more complex, involving other possibilities.
Of course, an underlying issue is the nature of terms - i.e. concepts.
For that, look at my Phenomenology, chapter 4.
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For your information, I have now written a whole essay on this topic, which you can read at:
This essay explains why the existential import doctrine of modern logic is really trivial. It gives equal weight to empty terms, putting them on a par with realistic terms. Whereas in actual logical practice, once a term is classed as empty it ceases to have any significance in scientific and other realistic thinking. Read the essay!
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