Boethius on the Trinity

In The Trinity is One God Not Three Gods, Boethius (c. 480–524), “the last of the Roman philosophers, and the first of the scholastic theologians,”¹ seeks to refute “the Arians, who, by graduating the Trinity according to merit, break it up and convert it to Plurality.”² The Arians affirmed that Jesus was divine in a sense, but of a lesser kind than the Father.³ On the contrary, Boethius argues for “the Unity of the Trinity” particularly as it is articulated in the Athanasian Creed, which states that “the Father is God, the Son is God, the Holy Spirit is God.”⁴ He argues that “Father, Son, and Holy Spirit are one God, not three Gods.”⁵ In what follows, I summarize Boethius’s argument, and argue that while his distinction between substantial and relational predication provides a powerful defense of the unity of the Trinity, it may prove inadequate when it comes to the Incarnation, wherein the Son takes on a human nature.

Boethius’s arguments for the unity of the Trinity use many distinctions from Aristotle. The first is a distinction between matter and form. Since physical things such as statues consist of matter (e.g., bronze) in a particular form, they contain plurality, for “each thing has its being from the things of which it is composed, that is, from its parts.”⁶ However, there is a crucial difference with God: “The Divine Substance is form without matter, and is therefore one, and is its own essence.”⁷ Since plurality comes only from matter, and God does not have matter, God cannot contain plurality. Therefore, God must be a unity.

Boethius then addresses a linguistic problem raised by the Trinity. He argues that although “we say God thrice when we name the Father, Son, and Holy Spirit,” this does not produce “a plurality of number” any more than “if I were to say ‘sun sun sun’ I should not have produced three suns.” Rather, “I should have spoken that many times of one thing.”⁸ Thus, the rules of language allow us to affirm that the Trinity is still a unity and not a plurality. And in case we think that Boethius’s example is flawed because the word “sun” is the same in all three cases, Boethius further clarifies that the same holds for “sword, brand, blade.”⁹ For, “one sword can be recognized in so many words.”¹⁰ However, here Boethius immediately adds a caution. Unlike in the case of sword, brand, and blade, in saying Father, Son, and Holy Spirit, “we are not using synonymous terms.” For “‘Father, Son, and Holy Spirit,’ though the same, are not identical.”¹¹ Thus, when asked, “Is the Father the same as the Son?” Boethius answers, “Not at all.”¹² The Father is God, and the Son is God, but the Son is not the Father.

It is here at the end of the third section that we might mention our first critique. After asking and answering the question above, Boethius makes a peculiar statement about the Father, Son, and Holy Spirit: “There is not, therefore, complete indifference between them; and so number does come in—number which we explained was the result of diversity of substrates.”¹³ This statement is puzzling here for two reasons. First, he has in fact not explained a “diversity of substrates” yet—at least not fully. Secondly, Boethius seems to directly contradict himself. For, in the previous section, he had just established that “form which is without matter will not be able to be a substrate” and that, since God is precisely form without matter, “in God, then, is no difference, no plurality arising out of difference … and accordingly no number either.”¹⁴ If there is “no difference” in God, then how can Boethius consistently say that there is not “complete indifference” between Father, Son, and Holy Spirit? What “number” or “diversity of substrates” does he have in mind?

It is not until the final two sections that we finally get an answer. Boethius distinguishes between substantial and relational predicates. Substantial predication, or “predication according to the substance,”¹⁵ describes an attribute of a thing considered by itself. Relational predication, on the other hand, does not “produce predication according to the essential property of a thing” and thus “it cannot be affirmed that predication of relationship by itself adds or takes away or changes anything in the thing of which it is said.”¹⁶ To illustrate the difference between the two, Boethius offers the example of being to the left or right of a person. “If I come up to him on the left, he becomes right, not because he is right in himself, but … in virtue of my approach.”¹⁷ Rightness, then, is not a substantial, but a relational, predicate. It does not change the thing itself.

Using this distinction, Boethius is finally able to consider “relationships to which all the foregoing remarks have been preliminary.”¹⁸ In short, “The Trinity is produced in the fact that it is predication of a relation, and the unity is preserved through the fact that there is no difference of substance … So, then, the substance preserves the unity, the relation makes up the Trinity.”¹⁹ The strange “substrates” we were puzzled about are in fact relational predicates, and the “number” was in the relations, not in the substance of God, which remains one in number.²⁰

Here we might raise another critique. Relations are usually between different substances—can something be related to itself? Boethius offers an incisive reply. He suggests that there are in fact reflexive relations such as being identical to oneself. “One must not forget that relative predication is not always such that it is always predicated with reference to something different, as slave is with reference to master … the relation in the Trinity of Father to Son, and of both to Holy Spirit is like a relation of identicals.”²¹ Yet another critique might wonder how we are to imagine this puzzling kind of relation. Boethius humbly responds: “If a relation of this kind cannot be found in all other things, this is because of the otherness natural to all perishable, transitory objects. But we ought not to be led astray by imagination, but raised up by pure understanding.”²² With God, then, we have reached the limits of human imagination. It is here that theology rightly transitions into doxology.

Even so, we might wonder whether Boethius’s metaphysical schema can account for the Incarnation. Recall that, for Boethius, God must not have any accidents,²³ for accidents entail multiplicity²⁴—and Boethius is highly motivated to avoid both, or open the door to Arianism. Thankfully, accidents arise only through matter,²⁵ and matter has nothing to do with God. Or does it? When the Son took on a human nature (John 1:14), was he not subjected to matter? In response, I suspect that Boethius might say that the Son’s human nature is merely a predication of relation—of the world’s relation to God—and so does not entail accidents in the substance of God. But, if the Son is the subject of "became" (egeneto) in John 1:14, is it really accurate to say that "flesh" (sarx) is not a substantial predicate of the Son? I must confess that I am still pondering this.

In closing, Boethius’s rigorous treatment provides many tools for defending the unity of the Trinity. While his emphasis on unity might seem to lessen the reality of Father, Son, and Spirit—they are mere “relational predicates”—Boethius’s determination to avoid the plurality of the Arians does make this emphasis on unity understandable. In any case, his use of relational predication is exceptionally powerful—and something that will be seminal for later scholastics.

[1] H. F. Stewart and E. K. Rand, “Life of Boethius,” introduction to Boethius, Theological Tractates. The Consolation of Philosophy., trans. H. F. Stewart, E. K. Rand, and S. J. Tester, Loeb Classical Library 74 (Cambridge, MA: Harvard University Press, 1973), xii. Unless otherwise noted, translations of Boethius are from this volume.

[2] Boethius, De Trinitate 1.

[3] “the Son … existed before times and ages fully God, only-begotten, unchangeable. And before he was begotten or created or appointed or established, he did not exist; for he was not unbegotten,” Letter of Arius to Eusebius, in Documents of the Christian Church, ed. Henry Bettenson (Oxford: Oxford University Press, 2011), 42.

[4] Boethius, De Trinitate 1.

[5] Boethius, De Trinitate 1.

[6] Boethius, De Trinitate 2.

[7] Boethius, De Trinitate 2.

[8] Boethius, De Trinitate 3.

[9] Boethius, De Trinitate 3.

[10] Boethius, De Trinitate 3.

[11] Boethius, De Trinitate 3.

[12] Boethius, De Trinitate 3.

[13] Boethius, De Trinitate 3.

[14] Boethius, De Trinitate 2.

[15] Boethius, De Trinitate 4.

[16] Boethius, De Trinitate 5.

[17] Boethius, De Trinitate 5.

[18] Boethius, De Trinitate 5.

[19] Boethius, De Trinitate 6.

[20] Technically though, for Boethius God is not a substance, but is supersubstantial (ultra substantiam).

[21] Boethius, De Trinitate 6.

[22] Boethius, De Trinitate 6.

[23] My reading of Boethius is that an accident is some attribute that you have, but might not have had.

[24] “In God, then, is … no multiplicity arising out of accidents,” De Trinitate 2.

[25] “Humanity receive[s] accidents … through the fact that matter is subjected to it,” De Trinitate 2.