Johnson, Aaron, and Jeremy Schott, eds. 2013. Eusebius of Caesarea: Tradition and Innovations. Hellenic Studies Series 60. Washington, DC: Center for Hellenic Studies. http://nrs.harvard.edu/urn-3:hul.ebook:CHS_JohnsonA_SchottJ_eds.Eusebius_of_Caesarea.2013.
14. How Binitarian/Trinitarian was Eusebius?
- The Binitarian structure of Eusebius’ theology was asserted by some German scholars, especially by Kretschmar and Hauschild. The new approach of Holger Strutwolf aims to reconsider this “standard view,” but needs further consideration itself.
- The pneumatology of Eusebius in his fight against Marcellus, especially in his Eccl. Theol. must be analyzed once again. My aim is to show that Marcellus was the first theologian of the fourth century who seriously raised the Trinitarian question. Thus, the impact of Marcellus (or the fight against him) produces the specific Trinitarian accent of the debate.
The German Discussion about Eusebius’ “Binitarism”
- An economical approach: the Trinity can only be understood in its close connection with the history of salvation;
- The large Origenistic group for whom it was familiar to speak of three hypostases;
- Binitarians. 
There is nearly no witness for the last group—except Eusebius. More precisely, we should say: the early Eusebius (who quoted Mt 28:19 without mentioning the Spirit), because Kretschmar observes that after the council of Nicaea in 325 Eusebius was well aware of the fact that he had to mention the Holy Spirit. He did so, e.g. in quoting Mt 28:19 in full, but his pneumatology is defective nonetheless.  In this respect his theology shifted away from Origen. Kretschmar suggests that this shift was caused by a modification of theological principles: While to Origen, cosmology and soteriology were deeply connected to each other, to Eusebius theology became mainly cosmology or a kind of metaphysical thinking.  To Origen salvation was accessible through the Son and the Holy Spirit. The Son had a double function for cosmology and soteriology, but the Spirit was mainly thought of as the way to salvation, i.e. pneumatology was just a part of soteriology. The shift from Origen to Eusebius, from cosmology and soteriology to cosmology alone, left no place for the Holy Spirit, while the cosmological significance of the Son was maintained and developed (especially in the apologetic discourse of the PE). This focus had a twofold effect: first, theology concentrated on the relation between Father and Son—with emphasis on the μονογενής the Holy Spirit having no place; second, the Holy Spirit was understood as the gift of God, not as God himself. Thus, Pneumatomachian theology was caused by Eusebius’ theology, but cannot be traced back to an earlier stage of theology (e.g. an old Binitarian tradition from former centuries). 
- Chapters 9–13: God as being and unique (Father)
- Chapters 14–19: The second cause (Son)
- Chapter 20: About the Three principal Hypostases (Holy Spirit as part of Trinitarian Theology)
- Chapters 21–22: The idea of the Good (≈ Father)
- Chapters 23–25: The ideas (≈ Son)
- Chapter 26: The demons (=> Holy Spirit)
The Impact of Marcellus for the Trinitarian Theology of Eusebius
- The aim of Book 11 is to show how Plato’s φυσιολογία fits the theology of the Old Testament, i.e. the philosophy of the Hebrews and especially Moses.  Thus, the structure of the following chapters is dominated by what we would expect from a handbook of Platonic philosophy. Accordingly, Eusebius starts with the Divine, then explains the second cause, the ideas, the demons, and the immortal souls. Finally, he arrives at the cosmology, the stars, the change of the world and its end (which for Eusebius is the resurrection and the last judgment). Thus, the structure of Book 11 is not the sequence of Trinitarian thought and anthropology, but an ontological hierarchy of beings. Of course, Eusebius compares the Platonic thoughts with the theology of the Hebrews, thus stating that according to the Hebrews only God is the truly Good and that the Hebrews refer wisdom, justice, etc., directly to the Logos instead of to the ideas. But this does not lead to a Trinitarian structure of the argument. The next chapter simply proceeds on to the next level of the Platonic hierarchy. Therefore, I doubt that the demonology in chapter 26 is caused by the intention to integrate the Holy Spirit into divinity.
- The Holy Spirit is only briefly mentioned in the context of Trinitarian theology. Eusebius, however, does not assert the divinity of the Holy Spirit in this short text. He explains that according to the Hebrews after Father and Son there is the Holy Spirit, the third in order that belongs to the Trinity.  That the Holy Spirit belongs to the Trinity is shown by the fact that the Holy Spirit is superior to all beings and creatures, established before all noetic beings by the Son, being the third one in comparison with the first cause, the Father.  Eusebius does not explain how divine or not divine this third component is. It belongs to the Trinity, but also to the noetic beings, it is superior, but at the same time, “the third.”
Eusebius quotes the famous passage of the Pseudo-Platonic letter 2 (ep. 2.312de)  which Clement used already in order to show that even Plato knew about the Trinity.  Then he adds that in addition to the first God there is the second cause and that the World-Soul is third, since the Platonists define the World-Soul as a third God.  He does not comment on this, but simply concludes his passage by saying that the divine scriptures describe the Trinity as a principle (ἐν ἀρχῆς λόγῳ). Then he gives a short note leading to the following section, in which the substance of the Good will be explained. 
Eusebius is very prudent in his statement about the Holy Spirit. He neither identifies it with the World-Soul nor does he reckon it as divine. He shows that what Plato described as a World-Soul and a third God can be compared with the Holy Spirit of Hebrew theology.
- The subject of chapter 26 is not the Holy Spirit, but demonology. The Holy Spirit is not at all present in this section. Eusebius starts with the statement that there are not only good powers but also bad ones, too. Exactly on this point, Plato follows the words of the Hebrews. Then he quotes a section of Nomoi (896de) where two World-Souls are mentioned, a good one and a bad one. There is no identification of the World-Soul with the Holy Spirit in this text, but the quotation is given in order to show that Plato knew about bad spirits. That is why Eusebius quotes Job 1:6–7: Even Scripture speaks about the devil and the angels. In his description of the angels, the Holy Spirit is not present. Thus, I doubt that we can take this passage as a pneumatological one. It is just a passage about angels and demons.
- Hypothesis A: The Logos went out from the Father and came to us (Jn 16:28—this biblical reference is missing in the apparatus of Klostermann and Hansen).
- Hypothesis B: The Holy Spirit went out from the Father (Jn 15:26) and he just preaches what he hears from the Logos (Jn 16:13–14).
- Conclusion: What proceeds (ἐκπορευόμενον) from the Father is some- times called the Logos, at other times it is called the Holy Spirit. Therefore, the Son and the Holy Spirit belong to the μονάς both in the same sense. This proves the mystery, i.e. that the μονάς was extended (πλατύνεσθαι) to a Triad, remaining identical to itself. Thus, God (as a Monad extended to a Triad) is indivisible. 
Marcellus adds two further arguments: first, if the Son says “Take the Holy Spirit” (Jn 20:22) and the Holy Spirit receives everything from the Son (Jn 16:13–14), it is clear that what the disciples have is this Monad-Triad (the Holy Spirit being the Logos);  second, if the Son and the Holy Spirit are two different persons (as Asterius said), either the Holy Spirit went out from the Father, thus having no need of any help from the Son, or he receives everything from the Son, thus having no need of any direct relationship to the Father.  Conclusion: Asterius mentions the three hypostases several times, but this is apparently wrong (i.e. against the biblical witness). 
- First, he concentrates on the verb ἐξεληλυθέναι:  Of course, going out does not show identity. The Son was eternally with the Father, then he was sent into the world; for this purpose he went out from the Father. The Holy Spirit was always standing around God’s throne (as the angels did), then he went out from the Father. Also others went out from God, e.g. the devil or an evil spirit. Thus, going out can be said about the Son and the Holy Spirit in a similar manner, but this does not mean identity.
- The difference between the Holy Spirit and the Son is shown by the Spirit’s operations:  various quotations, especially from the Gospel according to John, show that Christ spoke about the Holy Spirit as a different person. In particular, the announcement of the operation of the Holy Spirit as the “other paraclete” shows this difference. Jn 20:22 is not already the fulfillment of this announcement, but only the preparation, a kind of purification. 
- Both the Father and the Son sent the Holy Spirit;  this is not contradictory, but shows only that Father and Son agree in their will, i.e. the Son does the will of the Father. The Holy Spirit is sent in order to teach the Christians more than was possible in the lifetime of Jesus (because of the audience that followed “the Jewish lifestyle”). Even regarding the forgiveness of sins, the disciples received higher and “fuller” charisms after the Ascension of Christ. Just this surpassing of the Holy Spirit, announced by Christ, shows that the Holy Spirit is different from the Son. In all the announcements, the Son speaks of the Holy Spirit as of a different person.
It is in this context that Eusebius adds the famous sentence according to which the Holy Spirit is better and “higher” than all other noetic and rational substance, surpassing them in honor and glory (and that is why he is “bunched together” [συμπαρείληπται] with the Triad), but that at the same time he is less (ὑποβεβηκός) than the Son. This last sentence is not proven by the arguments given before, but leads to the following section:
- The Holy Spirit receives everything that he reveals from the Father and the Son.  He is dependent on both. Both, the Father and the Son, are a) spirit and b) holy, but this is no proof of their identity with the Holy Spirit, e.g. the angels are called “spirits,” too, but of course they are not equal to the Holy Spirit. The Holy Spirit has, however, a specific character, because he is the Paraclete. So we should preserve Mt 28:19 where all three (Father, Son, and Holy Spirit) are mentioned. Eusebius explains this by using 1 Cor 12:6–9. The Father is the origin and the donor of grace, the Son procures this by leading the Holy Spirit who distributes the charisms. This interpretation of 1 Cor 12:6–9 is directly dependent on Origen’s explanation of Jn 1:3 in the Commentary on John.  There Origen explains how the Spirit is a) caused by the Son, and b) is distributing the charisms to the saints. In order to explain how these two points fit each other, Origen developed the idea that Christ is characterized by many aspects of his divinity (ἐπίνοια) and that the Holy Spirit is exactly these aspects. In establishing (Origen uses ὑφίστημι here) the Holy Spirit, Christ gives just these aspects to him, so the latter is as it were the hypostasis of these aspects. Thus, the Holy Spirit is caused by Christ’s procuring his aspects as charisms for the saints. This puts both aspects (dependence and superiority) into one sentence. If we accept this Origenistic background of Eusebius’s interpretation of Mt 28:19 by 1 Cor 12:6–9, it is absolutely not surprising that Eusebius in the last step deals especially with Jn 1:3 and the subordination of the Holy Spirit.
- The Holy Spirit is not only led by the Son, but also caused by him according to Jn 1:3.  The Father decides who will receive grace, the Son leads the Holy Spirit, and the Holy Spirit distributes the charisms. The Son is not only the creator of the universe, but he also causes to subsist the Holy Spirit (of course in the sense of Origen’s explanation of Jn 1:3). So there is a clear order: above all, there is God the Father who is over all and through all and in all (Eph 4:6); the Son is the only begotten God (cf. Jn 1:18). The Holy Spirit, however, is neither God nor Son, but has his origin from the Father in a manner comparable to the Son, while being at the same time one of those things that is brought into subsistence by the Son (Jn 1:3). The real problem of this sentence is the word “God” that is used in it. It means either God the Father or it means God in general (as a category). Thus, either the Holy Spirit is not identical with the Father or he is not God or divine at all. Because of the juxtaposition of “nor Son” it seems more probable to me (pace Strutwolf  ) that this refers to God the Father (the article is missing only because so-called “predicate nouns” regularly have no article, cf. Jn 1:1). From my perspective it is far from being certain that Eusebius here denies the divinity of the Spirit. He is just stressing the dependence and the specific operation of the Holy Spirit in order to refute Marcellus who is accused of the heresy of Paul of Samosata and others in the following sentence (the conclusion mentioned above).
The result of this analysis is that Eusebius is forced by Marcellus to explain why and in what respect the Holy Spirit is different from the Son. This leads Eusebius to a seven-page pneumatological passage. In his pneumatology, he clearly follows Origen. Thus, exactly the same problem that Origen was dealing with reappears in Eusebius: the Holy Spirit is dependent on the Son, but in his operation he is dealing with a higher degree than just creation or rational beings (that is the area of the Son’s operation). Since the effect (in our case, the Holy Spirit) should not be higher than the cause (in our case, the Son), the higher value of the Spirit’s operation seems to be contradictory to his being caused by the Son. But just like Origen, Eusebius refers to the fact that exactly the soteriological function of the Holy Spirit is closely linked to his being brought into subsistence by the Son. The Holy Spirit is what Christ gives to the saints; he establishes the body of Christ by the charisms that are the aspects of Christ’s divinity.
- I. While he could use the ὁμοούσιος for the Son, he did not use it for the Spirit. For the Trinity as a whole, however, he could speak of μία οὐσία.
- II. Regarding pneumatology he applied Eusebius’s mention of the Spirit’s sanctifying function (of the angels, etc.) to the argument that exactly this high level guarantees that the Spirit is not a creature (though he did not use the word God in this respect). 
In this strategy, a certain measure of prudence is as present as the attempt to express definitely the divinity of the Holy Spirit. Exactly this strategy was widely accepted in 381.