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Mar 23, 2018 at 14:42 comment added Zuhair Al-Johar @JoelDavidHamkins most of what you are doing is to found Mereology in Set theory, or in founding set theory in some extension of Mereology (like by addition of a primitive singleton function on top of mereology). I'm doing neither here, I'm simply having both primitive relations and seeking to interpret rules of set theory by mimicry in Mereology. I didn't see that in ANY of the theories you've mentioned.
Mar 16, 2018 at 11:16 vote accept Zuhair Al-Johar
Mar 15, 2018 at 20:32 comment added Zuhair Al-Johar I read Lewis book on Parts of classes, I didn't see any real motivation for set theoretic axioms, he only explains membership using the singleton function on top of Mereology, he explains also Ur-elements, sets, classes, proper classes, etc.. but the rules of set theory he gives no real explanation of that stems from his mereology, actually in his account they are motivated by size principles, that's why he himself calls mathematics as size theory. Here you see a motivation whether direct (like the individual axioms of $\text{ZF}$ mentioned above) or indirect (like the case of replacement).
Mar 15, 2018 at 19:31 comment added Joel David Hamkins Thanks, Philip, I'm glad you like the results. I really like them, also, in part because they are mathematically interesting as well as philosophically relevant. In new work, with Ruizhi Yang, we are looking at other definable reducts of $\langle V,\in\rangle$, for example, to the unary union operator. This theory also is decidable, but if you have unary union and binary union, you can define singleton and subset and hence $\in$. It follows that binary union is not definable from unary union.
Mar 15, 2018 at 19:01 comment added Philip Ehrlich Joel, this a a remarkable set of results. Collectively, they seem to suggest that mereology is so close, yet so very far from being able to provide an adequate foundation for mathematics
Mar 15, 2018 at 11:23 history edited Joel David Hamkins CC BY-SA 3.0
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Mar 15, 2018 at 1:09 history answered Joel David Hamkins CC BY-SA 3.0