A large amount of work on Eternal Functional Subordination has been carried out in response to Tom McCall’s objection that
EFS implies a denial of homoousion. I personally think his argument is pretty solid – nevertheless I will leave you to decide whether you agree with it or not.
Here’s is McCall’s argument in a nutshell:
1)If Hard EFS is true, then the Son has the property being functionally subordinate in all time segments in all possible worlds.
2)If the Son has this property in every possible world, then the Son has this property necessarily. Furthermore, the Son has this property with de re rather than de dicto necessity.
3)If the Son has this property necessarily (de re), then the Son has it essentially.
4)If Hard EFS is true, then the Son has this property essentially while the Father does not.
5)If the Son has this property essentially and the Father does not, then the Son is of a different essence than the Father. Thus the son is heteroousios rather than homoousios.
This argument seems pretty solid to me. Nevertheless, I see at least one possible point of contention. This point of contention lies in premise (3). This is by no means an original thought – Andrew Naselli has pointed this out. The idea is that McCall might be conflating the word essentially with belonging to the essence. This may or may not be the case. What it ultimately boils down to is your answer to the questions – what makes something an essential property? And is an essential property the same thing as the essence of a thing? Whatever you make of those questions will determine whether or not you have problems with premise (3). My money’s on the notion that:
P is an essential property of an object o just in case it is necessary that o has P.
Or to put this in the language of possible worlds:
P is an essential property of an object o just in case o has P in all possible worlds, whereas P is an accidental property of an object o just in case o has P but there is a possible world in which o lacks P.
If we take this to be the definition of “essential” then it sure seems like there isn’t actually a problem with premise (3).