In a Christian context, debates about monotheism and trinitarianism seem to reduce to this: who are [or is] the Father, Son, and Holy Spirit, who or what is God, and how are these related to one another? Drake’s view is as follows:
There are three divine persons: Father, Son, and Spirit. To be divine is to be eternal, omniscient, good, just, etc. These are universals which may be predicated of the Father, of the Son and of the Spirit; that is, each is divine because there are a set of distinct, divine attributes which may be predicated of each of them. Why this is the case will be explained momentarily.
Whereas these attributes are what each has in common with the others, each is individuated from the others by his respective property or properties. So, for instance, the Father is eternally unoriginate, the Son is eternally begotten or generated from the Father, and the Spirit eternally proceeds from the Father.
Hence, the Father, Son, and Spirit must be distinct persons. To be a person is to possess a mind capable of reflexively indexing a certain set of propositions. So, for example, the reasons that the Father, Son and Spirit are distinct persons or minds is that only the Father can think “I am unoriginate,” only the Son can think “I am eternally begotten,” and only the Spirit can think “I eternally proceed.”
[These variances in reflexive thought do not imply that omniscience is impossible. The subject of the proposition "I am unoriginate" is, for the Father, "the Father," and both the Son and Spirit also assent to the proposition "the Father is unoriginate." Propositions are the meanings of declarative statements, and the meaning of the Father's thought "I am unoriginate" is synonymous with "the Father is unoriginate." Reflexive knowledge can accordingly be considered an indexation of propositional thought.]
Eternal generation and procession may be distinguishing properties, but they also point to the source of unity among the persons: the Father. It is the Father who communicates His divine nature, essence, or attributes in the Son and Spirit whose very persons are metaphysically grounded in the Father. This is not to say that the Son and Spirit are creations, however. Each is eternal and consubstantial with the Father in respect to His divine nature, for both persons causally extend from the Father necessarily rather than as an act of free will. And though eternal generation and eternal procession can be considered types of emanation or consubstantial extension from the Father, it is not Neoplatonic since such causality is a property of the Father alone. But the point is that the Father is the point of unity among the divine persons, not an abstract set of attributes which each person allegedly possesses of Himself. The Son and Spirit are not "autotheos." From this, Drake concludes that in the ontological as well as economic Trinity,
There is a subordination of persons but not of nature. The nature in the Father, Son and Holy Ghost is the same in character. However, the Father is the source of the Son and Spirit and all operation... Therefore, the Son is said to obey these commands and operations of the Father (John 10:18, Heb 10:7). The Son never commands the Father but the Father commands the Son. Jesus said in John 14:28 that the Father was greater than he was. The very terms Father and Son require a subordination of some kind.
It may be better, when first trying to grasp this view, not to think of the divine nature abstractly at all. There is certainly nothing wrong with the question, "what is the divine nature?" The divine nature is an idea – a proposition enumerating the attributes which must be predicable of an person in order for him to be divine – analogous to human nature. But neither divine nor human nature in themselves are minds or persons but attributes which identify divine or human minds or persons. Now, I may be said to be human and Jesus may be said to be divine, but in both cases the person is the subject.
As such, "God is three persons," "God is Triune," etc. are false. These propositions make the subject an impersonal divine nature and lead either to the view that the three persons are merely modes of God, which is the error of Sabellius, or to the view that the three persons are in some sense merely parts of God, which is unintelligible. It is no more proper to state that "God is three persons" than it is to state that "human is x number of persons."
This is a danger of considering the doctrine of the Trinity by beginning with the divine nature abstract from persons of whom it may be predicated. Hence, it is often the case that those who hold to the Western or Latin view will first ask “what” – not “who” – is God yet proceed to use personal [relative] pronouns in describing God’s attributes. This turns the divine nature into a person and either leads to a quaternity or a collapsing of the Trinity into [parts of?] one person.
The alternative to this conception of "numeric unity" is "generic unity" which in Drake's words, means that "the divine nature is generic in the sense that it defines the necessary predicates of three different things: three different divine minds." The only subjects to whom the genus "deity" can apply are the Father, Son, and Spirit. These persons are said to be united because of each the genus "deity" may be predicated, albeit with the qualification that the ground of this unity lies in the Father's eternal communication of this genus in the Son and Spirit.
The debate regarding generic and numeric unity is primarily about the ground of unity, though, of course, why one thinks the Father, Son, and Spirit may be said to be united will affect how one thinks they are united. Generic unity holds the Father as the principle of unity whereas numeric unity holds the divine nature as the principle of unity. The latter view, therefore, requires that the Son and Spirit are autotheos. Drake argues the contrary: "Aseity is not a divine attribute. It is a personal property of the Father. If Aseity is an divine attribute then this denies the eternal generation of the Son, which requires derivation."
The debate between numeric and generic unity is important because, for example, the view of the divine nature as absolutely simple presupposes that the principle, cause, origin, or source of unity among the Father, Son, and Spirit lies in the divine nature "itself" (numeric unity), whereas a view of the divine nature as allowing for real distinctions would be perfectly compatible with the Monarchy of the Father (hence, with generic unity). Absolute divine simplicity is problematic because it is unable to account for how men can participate in the divine nature (2 Peter 1:3-4) given that there are no real distinctions in it. In fact, if there are no real distinctions in the divine nature, some sort of Neoplatonic Monad seems to follow. Real distinctions in God's knowledge and attributes, for instance, are good and necessary to the perfection of the Trinity.
Given these considerations about individuation, personhood, the divine nature, unity, etc., what does "God" means? Drake writes:
I have found that the word “God” can mean at least 6 things in this discussion: 1. The Father/Monarchy; Concreted person; 2. The Divine Nature; abstract substance; or that an uncreated person possesses a divine nature 3. Godhead 4.Source of operation; 5. Auto-theos: that is uncaused 6. An indirect sense in that the Logos and the Holy Spirit are called God as they inter-dwell (perichoresis) and are consubstantial with the Father.
Drake usually uses definitions 1, 4, and 5 when referencing "God." So, for example, Jesus is referred to as the Son of God. Just as the Son is a person, “God,” in this context, is a person – namely, the Father. As the Nicene Creed states, “We believe in one God, the Father, the Almighty, maker of heaven and earth, of all that is, seen and unseen.” The one God is the Father. The Father alone is Monarch, autotheos, inoriginate, the principle of unity, etc. Drake doesn't use definition 3.
As for definitions 2 and 6, “God” may in this sense be predicated of the Son and Holy Spirit, but in these cases such is due the fact they are persons who are divine; that is, to say Jesus [or the Holy Spirit] is God is a reference to the essence communicated from the Father. Even in this sense, “God” is an adjectival predicate, not a subject.
The most serious charge against this position is that it implies tritheism rather than monotheism, and Christianity is a monotheistic religion. But this charge can be answered only when it is clarified who or what the "one God" is. On Drakes view, Christianity is monotheistic insofar as the Father is the only person of the Trinity of whom “God” can be predicated qua personhood (cf. definitions 1, 4, and 5): “On my Nicene view, being the one God is a hypostatic property of the Father, not a divine attribute.” This does not preclude the divinity of the Son and Spirit:
God is not three gods as in Tri-theism but God is the Father and with the Father are his Word and Spirit in whom the Father communicates the divine nature. There is only one God, one divine nature and one divine operation. God is the only cause though there are different agents of action in the world. Causality requires infallible operation to produce a uniform effect. The Father is this cause. God is static and immutable. Ad extra the action of God is one in that all things are different aspects of one eternal act. This eternal act is governed by the plurality of Ideas or Thoughts in God as his nature Ad Intra. This eternal act is good because it is in accord with his divine nature/thought affirmations.
Does this mean that on Drake's view, Christianity is tritheistic with respect to definitions 2 and 6 for "God"? Yes. But since whenever Scripture references the "one God" it is always with reference to the Father, this is irrelevant. In the contexts of Scripture in which monotheism is emphasized, only definitions 1, 4, and 5 are applicable anyways. Where, then, is the error? It's principle of individuation coupled with it's rejection of an abstract divine nature as the principle of unity among the Trinity precludes Sabellianism. It's rejection of the Son and Spirit as created in favor of the monarchy of the Father as presented in Scripture, the original Nicene creed, and the Cappadocian Fathers precludes Arianism. Unitarianism appears to be an undefined catch-all which, if applied in this instance without accompanying counter-arguments, would signal a pejorative hit-and-run tactic.
None of this is meant to imply I have no more questions or concerns about this view. But then, those questions or concerns are not solely related to Trinitarianism. For instance, I still have questions about which theory of time is true or whether the idea of multiple possible worlds is intelligible, and the implications of Drake's strict view of the Trinity would seem to demarcate what possibilities are live options. But then, I'm going to have the same or similar questions with respect to any Trinitarian position, and I'd probably have further questions specifically relevant to that Trinitarian view.
To conclude then, Drake's view is the most coherent I have read. I would recommend his posts on Triadology (cf. here, here, here, and here), particularly for the sections of Scriptural support for his preference in using definitions 1, 4, and 5 for "God."
* Personal note: a thanks to Drake for reviewing this post and making some suggestions.