According to the answers here and here, the term person means "an individual substance of a rational nature".

According to trinitarian theology, the triune god exists as three consubstantial persons consisting of one substance.

Does this mean the triune god exists as three individual substances of a rational nature, consisting of one substance of an irrational nature, in which neither nature is divided so that each are fully rational and irrational?


The Divine Substance (a.k.a. God) is supremely rational, as long as we understand the term rational to mean “capable of intellectual knowledge.”

As I mentioned in my answer to the O.P.’s question regarding person and substance, the Divine Substance (God) is perfectly identical with each one of the Persons.

The Persons are really distinct from one another, because they consist of the very relations of origin that subsist in the Godhead. However, there is no real distinction between Person and Substance. (In God, individual and universal substance coincide perfectly.)

(It is important to recall that the notions of person and substance—which strictly speaking apply only to creatures—are applied very improperly to God. That is why theses affirmation sound strange to us.)

As I mentioned in my previous answer, substance can have two slightly different connotations. For an Aristotelian like me, “substance” primarily means individual, concrete beings, like trees, flowers, stones, and human beings. Secondarily it can mean the common or universal kind of thing something is: for instance, tree-kind, flower-kind, stone-kind, and mankind. (For a Platonist, the priority is reversed—but for our purposes the fundamental idea is the same.) Also, “substance,” “essence,” and “nature” are basically synonyms for the ancient Greeks.

Now, Boethius’ definition for person, as the O.P. correctly mentions, is “individual substance with a rational nature.” We are, therefore, dealing with the two meanings of substance that I just mentioned above. Boethius is affirming, in effect, that a person is a concrete being that belongs to a particular genus or kind of being: namely those with the capacity for intellectual (rational) knowledge.

Boethius’ definition, as I mentioned, applies properly to creatures. God is beyond creaturely genera and species. However, He does possess to an infinite degree the capacity for intellectual knowledge (i.e., He is omniscient).

Therefore, both the Divine Nature or Substance (a.k.a. God) and the Divine Persons (who are, as I have mentioned, each perfectly identical to the Divine Nature) are not only rational but supremely rational.*

Hence, irrationality has no part whatsoever in God. Moreover, God is one Substance: the Persons do not divide the one Substance in any way whatsoever. In no way can He be considered three Substances.

* Note that in classical Scholastic lingo the term “rational” can be taken in a strict sense and in a broad sense. In the strict sense, “reason” and “rationality” refer to the particular kind of intellectual knowledge that we human beings possess. Our intellects are discursive; that is, we have to use concepts, enunciations, and argumentations to arrive at knowledge. Not all intellects are like that, however. For instance, angelic intellects are intuitive. In the broad sense, however, “rational” is a synonym for “intellectual.” That is what Boethius means by it.

  • Thank you for the answer. I thought this might mean the triune god is the fourth person of the triune god, but now I'm really confused. It seems like words are being used, only to be told that these words do not apply to the triune god, but then the words continue to be used as though they are still relevant. When you say "However, there is no real distinction between Person and Substance" this sounds like Sabellianism to me. Now I'm interested to know how this question will be answered.
    – Cannabijoy
    Oct 18 '16 at 9:09
  • The terms are applied analogically—which is to say, substance and person in God bear some resemblance to those realites among creatures (i.e., inasmuch as God is the Creator and Exemplar of those realities in creation). Saying that the Substance is a fourth entity in God is the heresy of Gilbert de la Porrée. Sabellianism would say that there is no distinction among the Persons. The orthodox position is to say that Nature and Person are perfectly identical, but the Persons are really distinct. Oct 18 '16 at 9:53
  • I don't know. If I use these terms improperly like trinitarians do, but still act as though they are relevant, then it seems we have one rational substance (god), existing as three distinct rational substances which are all fully the one rational substance (person/mode), and the only difference between the three is their "relation of origin". Relation of origin sounds like a fancy phrase for "role".
    – Cannabijoy
    Oct 18 '16 at 11:57
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    @anonymouswho It might help to recall that the Persons are actually the relations of origin. The Father is Fatherhood; the Son is Generation, and the Spirit is Procession. A relation is not the “role” of the Person; it is His ontological condition. The Father is without origin, the Son receives the (complete and undivided) Divine Nature from the Father, and the Spirit receives the (complete and undivided) Divine Nature from the Father through the Son. Oct 18 '16 at 12:54
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    @anonymouswho Also, “improper” does not mean “irrelevant.” God is the creator of His creatures. So person and substance in creatures are a true reflection or manifestation of something that God has to an infinite degree in Himself. For instance, we affirm rightly that God is good. But the only goodness we have direct experience of is goodness among human beings. God is not good in precisely that way; rather, He is infinitely more good than any mere man could possibly be: so much so, that He would be better characterized as Goodness Itself. Oct 18 '16 at 13:05

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