This is in reference to an old discussion with Bruce Nielson (who is a Mormon), which still seems to influence some of the things he says about the traditional Christian doctrine of the Trinity (though I don’t claim I’m the only influence on his thoughts on that topic).
Bruce objects to the concept of “substance” in general, holding it to be meaningless, at least as far as he can make out. In particular, he apparently objects to traditional Trinitarians using the word “substance” to distinguish the traditional Trinity (“TT”) from the LDS Godhead (“LG”); the former being considered a single substance, the latter multiple substances.
Specifically, I think it offends him that some TT adherents seek to exclude Mormons from the Christian fold based on this asserted difference in our beliefs. The fact that “substance” has no meaning that he can understand — and if it does have an objective meaning, it’s one that TT adherents by-and-large are unable to articulate clearly anyhow — makes it appear to Bruce that we have a choice in the matter: We could choose to understand the word in a way which allows the LG to be a single substance as well, and therefore not in conflict with the TT in any essential way.
Of course, this is my interpretation of various remarks of his over the past few years. I will not be surprised to find that Bruce thinks I have got him wrong on various points (that would be par for the course); if so, I welcome any corrections he may choose to offer.
Anyway, in a comment to this post of Bruce’s, I tried to explain that God is not actually considered a substance in the Thomist scheme of things. This is not something I had explained to Bruce before, since it only became clear to me after the last installment of our discussion. I thought I would take this opportunity to elaborate on it.
Here is an excerpt from St. Thomas’s answer to the question, Whether God is contained in a genus? Specifically, whether he is contained in the genus “substance”:
Objection 1 [the opposing argument]. It seems that God is contained in a genus. For a substance is a being that subsists of itself. But this is especially true of God. Therefore God is in a genus of substance [thus God is a substance].
* * *
I [St. Thomas] answer that, … That [God] cannot be a species of any genus may be shown in three ways.
* * *
Secondly, since the existence of God is His essence, if God were in any genus, He would be the genus “being”, because, since genus is predicated as an essential it refers to the essence of a thing. But the Philosopher has shown (Metaph. iii) that being cannot be a genus, for every genus has differences distinct from its generic essence. Now no difference can exist distinct from being; for non-being cannot be a difference. It follows then that God is not in a genus.
Thirdly, because all in one genus agree in the quiddity or essence of the genus which is predicated of them as an essential, but they differ in their existence. For the existence of man and of horse [both of which are in the genus "animal"] is not the same; as also of this man and that man [each of which has a separate existence]: thus in every member of a genus, existence and quiddity–i.e. essence–must differ. But in God they do not differ, as shown in the preceding article. Therefore it is plain that God is not in a genus as if He were a species.
Reply to Objection 1. The word substance signifies not only what exists of itself–for existence cannot of itself be a genus, as shown in the body of the article; but, it also signifies an essence that has the property of existing in this way–namely, of existing of itself; this existence, however, is not its essence. Thus it is clear that God is not in the genus of substance.
[A substance is a thing which exists of itself (meaning it's not a composite of other things, nor a part of something else), but its existence is not its essence, as it is, again, in the case of God. Therefore God is not a substance.]
When we speak of God being three Persons but one substance, we are using “substance” analogously. To use a word univocally means to use it in the same sense always; to use a word equivocally means to use it in different senses; to use a word analogously means to use it in a sense that is the same in some ways, but different in other ways. Thus for example, God creates and we also create. But we don’t create in the same way God creates, since we can only form things out of already existing things, whereas God is not subject to that limitation.
In the same way, we use the word “substance” in speaking of God, in a way that is analogous to the way in which we use it when referring to natural substances: In the sense that God, like a natural substance, is a single, unified being, and exists of itself, i.e. is neither a composite of other beings, nor a part of any other being. (The difference between God and a natural substance, is that a natural substance is a composite of form and matter; and also that in a natural substance, essence and existence are distinct, whereas in God they are identical, as explained above.)
I don’t have a problem (since it’s none of my business) with Mormons or any particular Mormon believing that the Father, Son and Holy Spirit are a single entity of some form, composed of three individual beings completely united in thought and will — however this then would make them not collectively a substance, since a substance is not composed of other beings; or on the other hand, believing that they are a single being neither composed of other beings nor a part of any other being — in which case their belief would mirror the TT in that they would be a single substance (analogously?). However, they would then be excluded from being united with other gods which might later come into existence, as a single substance — since again, that would make them a composite and therefore not a substance.
Of course, I can admit that the LG is analogous to the TT, since they are the same in some ways, and different in other ways. I just don’t see how I could call them both “Trinity” or “Godhead” univocally, since I would mean something different in each case.
I don’t say any of this for the purpose of excluding Mormons from the Christian fold. As explained elsewhere, I believe Mormons (as well as unbaptized Protestants) are outside the fold due to lacking valid baptism, as taught by the Catholic Church. Since for me that disposes of the issue, the way Mormons describe the Godhead is irrelevant to the question of whether or not they are properly called Christians.