Kalekas in Historical Context

Manuel Kalekas, known for his expertise in rhetoric and theology, played an important role in the development of Byzantine theology during the fourteenth and fifteenth centuries. Although Kalekas would consistently identify himself as a son of Constantinople, the name Kalekas itself is originally of Slavic origin. Although sometimes he is identified as a nephew of Patriarch John XIV Kalekas, there is no historical evidence to establish a firm family connection between these two men. Nonetheless, the fate of Patriarch John XIV would impact Manuel greatly.^{Footnote 7} In 1347, a council assembled by Empress Anna released Gregory Palamas from prison and deposed Patriarch John XIV. John XIV Kalekas died in prison, and Manuel Kalekas would spend his formative years in fear of persecution as a result of these events.^{Footnote 8} When John VI Kantakuzenos entered Constantinople, he quickly called a synod to confirm his actions, and by 1351 a council was held that not only vindicated Palamas but declared his teaching on divine energies to be normative for the Byzantine Church. This development prompted a variety of different reactions from those unsympathetic to this doctrine. Nicephoros Gregoras opposed the teaching vigorously, which eventually ended in his imprisonment. A young Byzantine diplomat named Demetrios Kydones (d. 1397/8), who would later come to play a significant role in Kalekas’s life, began a thorough study of theological sources, including Latin authors like Aquinas.^{Footnote 9} We know from his later correspondence that Manuel Kalekas retreated to a monastery during much of the period following 1351 and that he did not return to Constantinople for many years. Although not a monk, he seems to have had an arrangement that allowed him to live as an associate of the monastery.^{Footnote 10}

During the 1350s, Aquinas’s works became increasingly available in Constantinople and wider Byzantium. Although some extracts from the Summa theologiae were available in Greek translation as early as 1305, more complete translations of this work and the Summa contra gentiles were available by the end of the 1350s. Demetrios Kydones’s translation of the Summa contra gentiles—which was completed in 1354—was particularly influential for Byzantine receptions of Aquinas during the second half of the fourteenth century.^{Footnote 11} Kydones would also translate portions of the Summa theologiae as well, completing the Prima pars, the Prima secundae, and the Secunda secundae.^{Footnote 12} Some elements of the Tertia pars would become available in Greek as well.^{Footnote 13} Although perhaps not as ubiquitous as his translation of the Contra gentiles, the manuscript tradition of Kydones’s translation of the Prima pars of the Summa theologiae suggests that this text was also widely circulated.^{Footnote 14}

In 1390, Manuel Kalekas returned to Constantinople on the advice of a friend in order to found a school of rhetoric, structured around the classical works of Greek antiquity.^{Footnote 15} Although his school was not a success, during this time Kalekas came into contact with other like-minded Byzantine intellectuals, such as Demetrios Kydones, to whom he wrote in 1391. It is difficult to overstate the import of Kalekas’s acquaintance with Kydones and his circle in Constantinople. His contact with this group brought him into conversation with a group of Byzantine intellectuals who shared his interests and sympathies. However, Kalekas’s familiarity with Thomism probably began before his return to Constantinople. His De fide deque principiis fidei catholicae (the subject of this study) was the first of his theological writings and was probably begun prior to 1391. This text reflects a deep awareness of the works of Aquinas that had been available in Greek translation since the 1350s, thanks in large part to Kydones.^{Footnote 16} From 1391 to 1396, Manuel studied under Kydones, benefiting greatly from his expertise; his study of Aquinas under Kydones clearly influenced the final version of De fide, which was completed before the end of 1396.^{Footnote 17} While studying under Kydones, Kalekas would also become acquainted with a number of other students who shared his interests. Among these new associates were the brothers Maximos, Theodore, and Andrew Chrysoberges, all three of whom studied Aquinas under Kydones during this time.^{Footnote 18} In particular, Kalekas’s friendship with Maximos Chrysoberges was an important influence for Kalekas between 1391 and 1396, and their friendship would continue for many years even after both had left Constantinople.^{Footnote 19}

In 1396, the declarations of 1351 that had enforced conformity to Palamite doctrine were renewed. By the end of this year, Kalekas and many other members of the Kydones circle would seek refuge with the Genoese at Pera, in order to escape the persecution of the Palamites.^{Footnote 20} Judging from his letters, the events seem to have been an important moment in Kalekas’s life, sparking a formal rupture with the Byzantine Church.^{Footnote 21} From Pera, in the fall of 1396, Kalekas wrote to Emperor Manuel II Palaeologus, lamenting the fact that his opposition to Palamism had ostracized him from the church in Byzantium and effectively barred his entrance into religious life.^{Footnote 22} It is not clear if the publication of De fide, which does not affirm the Palamite teaching on the Trinity, was the immediate cause of any unwanted personal attention.^{Footnote 23} Kalekas remained at Pera, staying with the Dominican community there from 1396 to 1399, and likely entered into full communion with the Roman Church in 1398.^{Footnote 24} Kalekas subsequently moved to Crete in 1400, where he continued to work with Maximus Chrysoberges and his brothers, Theodore and Andrew. From 1401 to 1403 Kalekas lived at the Benedictine monastery in Milan, where he completed De processione Spiritus Sancti and began Adversus Graecos. During this time, he also completed translations of Boethius’s De Trinitate and Anselm’s Cur Deus homo.^{Footnote 25} From here he moved to Lesbos, where he took the habit of the Dominican order and died in 1410.^{Footnote 26}

Aquinas as a Source for De fide

Manuel Kalekas’s De fide (1396) is intended to be a comprehensive presentation of Christian doctrine, covering theological topics from the doctrine of God to the seven sacraments. Although Kalekas quotes liberally from Byzantine and Greek patristic sources, the structure of the text itself reflects the influence of Latin scholasticism. The first chapter of De fide takes the form of a short methodological introduction to the work.^{Footnote 27} Following this, Kalekas deals with “the one God” (Περὶ τοῦ ἑνὸς Θεοῦ) in chapter 2, and “the one God as Trinity” (Περὶ αὐτοῦ τοῦ ἑνὸς Θεοῦ, ὅς ἐστι Τριάς) in chapter 3.^{Footnote 28} Subsequent chapters discuss the image of the Trinity in creation (ch. 4), the incarnation of the Word according to Scripture (ch. 5), the seven sacraments (ch. 6), the fittingness of the incarnation according to reason (ch. 7), the future resurrection of the dead (ch. 8), and the future restoration of all things (ch. 9).

In addition to the general influence of Latin scholasticism, more specific parallels with individual Thomistic texts can also be discerned. At the outset, we notice that the methodological introduction found in the first chapter of De fide stresses Christ as a wisdom figure in a way that is similar to the first question of the Contra gentiles.^{Footnote 29} Further, the treatment of christology according to scriptural proof in chapter 5 and subsequently according to rational fittingness in chapter 7 echoes Aquinas’s division of this subject in the Contra gentiles.^{Footnote 30} Gouillard has argued that chapter 3 of De fide (which concerns us here) is dependent on Aquinas’s Contra gentiles, noting a number of parallels between the fourth book of the Contra gentiles and this chapter of De fide.^{Footnote 31} Without disputing these similarities, there are also reasons to suspect that Aquinas’s Summa theologiae—a text also available to Kalekas in Greek translation—influenced the structure and content of De fide, and Kalekas’s account of trinitarian procession specifically. The structure of the first four chapters of De fide—including Kalekas’s treatment of the Trinity—bears a strong resemblance to the structure of the corresponding sections of the Prima pars of the Summa theologiae. Like De fide, the first part of the Summa theologiae begins with a methodological introduction (q. 1), followed by a treatment of God according to the transcendental qualities of oneness, truth, and goodness (qq. 2–26); Aquinas begins his tract on the Trinity against this backdrop (qq. 27–43). By contrast, although the Contra gentiles does deal with methodology and the one God in book 1, it does not take up the subject of trinitarian procession until its fourth and final book.

The internal structure of the third chapter of De fide further reinforces the impression that a certain parity exists between De fide and the Summa theologiae; Kalekas begins this chapter by invoking the examples of the Arian and Sabellian heresies to frame his treatment of the Trinity.^{Footnote 32} Likewise, at the beginning of his own treatment of the Trinity in question 27 of the first part of the Summa theologiae, Aquinas uses the same examples to illustrate the dangers of describing the procession and distinction of the trinitarian persons in a way that results in either a difference of substance between the persons (Arianism) or a modalistic account that effaces the distinction between them (Sabellianism).^{Footnote 33} In De fide, Kalekas introduces orthodox trinitarian theology by framing his argument in a way that resembles the structure of Aquinas’s approach in question 27. Like Aquinas, Kalekas argues that trinitarian orthodoxy is found somewhere between the extremes of Arianism, which leads to a triad of essences (τρεῖς οὐσίας), and Sabellianism, which denies the trinity of persons (τρία πρόσωπα).^{Footnote 34} For Kalekas, Sabellianism offers a purely modal distinction (ποτὲ μὲν ὡς Πατέρα φαίνεσθαι, ποτὲ δὲ ὡς Υιόν, ποτὲ δὲ ὡς Πνεῦμα ἅγιον) between the Father, Son, and Holy Spirit. In contrast to this error, Kalekas affirms the unity of essence that unites the three distinct persons. In this understanding, God is indeed one essence and three persons (μία οὐσία, πρόσωπα δὲ τρία).^{Footnote 35} While the doctrinal content of this teaching may be unsurprising, the structural apposition of Arianism and Sabellianism in Kalekas’s argument mirrors the way in which Aquinas introduces these same doctrinal issues in question 27 of the first part of the Summa theologiae.^{Footnote 36} Conversely, no single text in the Contra gentiles provides a similar structural parallel.^{Footnote 37} Further, in addition to this structural similarity, Kalekas’s emphasis on the unity of the divine essence in the context of trinitarian procession is also aligned with the way in which Aquinas situates the question of trinitarian procession in the larger context of the first part of the Summa theologiae, where the beginning of Aquinas’s treatment of the Trinity in question 27 is framed against the backdrop of the unity of the divine essence that Aquinas works to establish in questions 3 through 26 of the Prima pars. At the beginning of his treatment of the Trinity in question 27, Aquinas continues to underscore the importance of this issue, emphasizing the risk of disrupting the unity of the divine essence through deficient conceptual accounts of the Trinity.^{Footnote 38} As we have seen, Kalekas’s teaching on trinitarian procession in chapter 3 of De fide is also preceded by his treatment of the unity of the divine essence in chapter 2. Like Aquinas, Kalekas continues to reference the unity of the divine essence in chapter 3 as he moves to give an account of trinitarian theology itself.^{Footnote 39}

The presence of structural parity, however, does not exclude the possibility of conceptual tension. Even within the context of these textual parallels, Aquinas and Kalekas propose different conceptual accounts of the way in which the distinction and procession of the trinitarian persons should be described. What is at issue here is the utility of the language of causality. While both Kalekas and Aquinas identify the importance of causality in this context, Aquinas is critical of its use, while Kalekas advocates for it. In question 27, Aquinas rules out two forms of causality, associating them directly with the errors of Arius and Sabellius. For Aquinas, the concept of procession should be said of the divine persons only after the forms of causality that he has associated with Arianism and Sabellianism are rejected. Kalekas takes the opposite approach, however, explicitly using αἴτιον to describe the relationship of the Father to both the Son and the Spirit in a way that he claims avoids the same errors of Arius and Sabellius.^{Footnote 40} Beginning with a warning against these two trinitarian errors, Kalekas describes the Father as the “cause” of the Son and the Spirit, who are referred to the Father by begetting (γεννητός) and procession (ἐκπορευτός), respectively.^{Footnote 41} Kalekas’s account of trinitarian procession culminates in his description of the Spirit’s procession through the Son. In defense of this formulation, Kalekas cites the authority of the Seventh Ecumenical Council, held at Nicaea in 787.^{Footnote 42} Despite Kalekas’s interest in Latin sources, the absence of the filioque should not surprise us here. Although dialogue between the Byzantine East and Latin West continued during this period over the filioque and church union, this aspect of Latin theology was not generally incorporated by the Byzantines during Kalekas’s time.^{Footnote 43} Although Kalekas will defend this position in his later writings,^{Footnote 44} in De fide he argues that the procession of the Spirit through the Son follows from the causal model he first adopted to describe the distinction-in-unity of the divine persons.

Although a degree of conceptual tension seems to exist between Aquinas and Kalekas on the subject of causality, not all tensions necessarily reduce to contradictions. In this case, reading De fide and the Summa in their proper historical contexts can mitigate this tension significantly. To understand the divergence between Aquinas and Kalekas on this point, it is helpful to distinguish between theological doctrine itself and the theological and philosophical traditions that are used to explain and defend this doctrine. Considered doctrinally, in the context of post-Nicene orthodoxy, the simple rejection of Arianism and Sabellianism is unremarkable—what shows the influence of Aquinas in this case is not so much that Kalekas rejects Arianism and Sabellianism in a generic sense, but the fact that the methodology and structure of Kalekas’s approach to trinitarian procession in De fide mirrors Aquinas’s approach to the same subject in the Summa. As has been shown, both Kalekas and Aquinas begin with the unity and simplicity of the divine essence and introduce the notion of personal distinction and procession in the Trinity against this backdrop, portraying Arianism and Sabellianism as doctrinal errors that describe the Trinity in a way that compromises the unity of the divine essence. This structural similarity suggests that the convergence between Kalekas and Aquinas is not merely doctrinal in the abstract: in this case, Kalekas has also absorbed something of the theological methodology of Aquinas’s Summa as well, and of the theological tradition that it represents.

While it is clear that Aquinas has influenced Kalekas in important ways, neither the Summa nor De fide can be properly understood without reference to the historical context in which each was written. Acknowledging a difference of historical context between the Summa and De fide does not undermine the claim that the former text has exerted a real influence on the latter—rather, an awareness of contextual difference enables a more accurate understanding of the true nature and extent of this same influence. All subsequent receptions of texts take place in historical contexts that differ from the one in which the text received was originally authored. Even in the later reception history of Aquinas in the Latin West, an awareness of historical context is important when approaching subsequent engagements with Aquinas. In a similar way, the Byzantine context of Kalekas and the Kydones circle necessarily affects the way in which Aquinas is received. Therefore, the following section will study the relationship between Kalekas’s teaching in De fide and existing theological paradigms in Byzantium.

Kalekas and Existing Byzantine Traditions

Kalekas was not the first Byzantine theologian to use the language of causality to describe the procession and distinction of the trinitarian persons. In the 1270s, the unionist Patriarch John Bekkos promoted a causal approach to trinitarian procession. Explicitly acknowledging the substantial unity of the three trinitarian persons, in his De unione Bekkos used causality to explain the procession of the Spirit from both the Father and the Son, in a manner that he argues is consistent with the doctrine of the Roman Church.^{Footnote 45} In many ways, Bekkos’s approach builds on Cappadocian sources that were in circulation in Byzantium at this time. Gregory of Nazianzus and Gregory of Nyssa both used causal language explicitly to distinguish the procession of persons in the Trinity and both were influential sources for thirteenth-century Byzantine theology.^{Footnote 46} Among the Cappadocians, however, it seems that Basil of Caesarea was particularly influential for Bekkos.^{Footnote 47} Basil distinguishes between principal and instrumental causality, naming the Son as an instrument or tool (such as a hammer) in relation to the Father as craftsman.^{Footnote 48} For Basil, the Father creates through the Son operating as a preceding cause.^{Footnote 49}

Although not unknown in the East, relational accounts of trinitarian procession were dominant in the Latin West, largely due to the influence of Augustine. In his De Trinitate, Augustine used the category of relation to distinguish the persons of the Trinity without introducing a distinction of essence or substance.^{Footnote 50} Since the late thirteenth century, a Greek translation of Augustine’s De Trinitate had been available in Byzantium, and Kalekas would have had access to this through Demetrios Kydones, who owned a copy of this translation.^{Footnote 51} As a received text in the Byzantine East, therefore, De Trinitate was already being incorporated into the Byzantine theological tradition and the work of the Kydones circle during Kalekas’s time in Constantinople. For his part, Kalekas is not only aware of Augustine’s arguments but actively references them in De fide. In a demonstration of intellectual creativity, Kalekas argues that causal and relational accounts of the Trinity can be understood as compatible, finding texts from both Basil of Caesarea and Gregory of Nazianzus that could indicate that the causal relationship between the divine persons is fundamentally relational.^{Footnote 52} Without citing Augustine explicitly, Kalekas discusses the possibility of opposing relations distinguishing the divine persons, even as he situates this conceptually against the larger backdrop of causality.^{Footnote 53} Nevertheless, Kalekas’s account of trinitarian procession and personal distinction remains strongly indebted to the concept of causality: in the end, Kalekas will insist that only causality can adequately distinguish the divine persons.^{Footnote 54}

Concerning the influence of Latin sources like De Trinitate on De fide, Kalekas’s intentions in this regard are perhaps best understood in the context of the existing Byzantine unionist tradition. Like Bekkos before him Kalekas attempts to show that the Augustinian relational approach can be understood within the categories of Byzantine theology, thus providing a means of understanding Augustinian trinitarian theology in the language of the Byzantine East. Because De fide is a text written for a Byzantine audience, something of this same methodology is discernable in Kalekas’s approach to Aquinas as well. Instead of addressing himself to Parisian scholastics, Kalekas offers an account of trinitarian procession from within the Byzantine tradition, even as he allows himself to be influenced by some elements of Aquinas’s thought. Understood in this way, Kalekas’s appeal to causality in this context seems not to be a rejection of Aquinas so much as an appeal to the conventions of existing Byzantine theology.

Aquinas on Causality and Creation

In order to better understand the relationship between Aquinas and Kalekas on the question of causal procession, it is important that Aquinas’s account of trinitarian procession be understood on its own terms and within the context of existing Latin theological traditions. Like many thirteenth-century Latin scholastics, the influence of Augustine is clearly discernable in Aquinas’s trinitarian theology. Although Aquinas will engage some ideas from the Greek fathers later in his treatise on the Trinity, the conceptual elements that actually structure Aquinas’s account of procession at the outset of this treatise in question 27 appeal primarily to authorities and to philosophical concerns internal to the Latin tradition. Understood in this context, Aquinas’s rejection of certain causal accounts of procession in question 27 should not be misconstrued as a reference to the Cappadocians but seen rather as a means of jettisoning certain philosophical assumptions about the concept of procession that would make it impossible to understand a relational account of trinitarian procession in an orthodox way. Although Aquinas associates certain forms of causal procession with Arianism and Sabellianism in question 27, in contrast to these errors Aquinas also begins to deploy an understanding of trinitarian emanation that is not only doctrinally orthodox but implicitly Augustinian. To describe the doctrine of trinitarian procession accurately, Aquinas invokes the Augustinian concept of the word of the heart: although it proceeds from the person in understanding, it remains within him.^{Footnote 55} Building on this, in question 28 Aquinas explicitly introduces an account of trinitarian relationality that is indebted to Augustine’s, arguing that the real distinction between the divine persons results from the oppositional qualities of their relations.^{Footnote 56} Here, Aquinas describes four real relations resulting from the internal processions of intellect and will, from each of which two opposite relations arise.^{Footnote 57}

Although Aquinas draws on the resources of the Latin-Augustinian tradition to give an orthodox account of the doctrine of trinitarian procession, his rejection of Arianism and Sabellianism in question 27 enables his description of the relational distinction of the divine persons in question 28 by eliminating a certain kind of conceptual error that would associate the concept of procession with the limitations and finitude of creation. Because the divine persons are eternal and unchanging, the internal processions that provide the basis for their real distinction must also be eternal and not subject to change of any kind. With this in mind, any account of procession that might imply a sense of contingency or limitation must be eliminated. In question 27, Aquinas uses causality to identify certain specific forms of causal procession that imply these limitations. In the case of Arianism, Aquinas argues that, when the relation between the Son and the Father is described causally, the Son is implicitly described as a creature. Likewise, Sabellian modalism represents a different attribution of created limitation to divinity, in which the change and historicism that is characteristic of creation is attributed to the divine person who proceeds.^{Footnote 58} In the context of question 27, Aquinas’s response to the first objection makes it clear that in this particular context, Aquinas intentionally uses the notion of causal procession to identify certain ways of thinking about procession in general that must be actively eliminated if we are to discuss the specific reality of divine procession. Although the objector asserts that no form of procession can be attributed to God because the concept of procession itself necessarily implies exterior motion to another, Aquinas argues that the objector’s account of procession in general actually applies only to causal accounts of motion in space.^{Footnote 59} By rejecting those “causal” forms of procession that imply the limitations of created being in question 27, Aquinas is able to develop the remaining notion of uncreated procession using the Augustinian doctrine of relation in question 28.

For Aquinas, the connection between causal procession and the concept of creation that appears in question 27 is echoed in his treatment of creation later in the first part of the Summa (qq. 44–49). In question 44, Aquinas uses the language of causality to describe the emanation of creatures from God as a form of procession that differs from the procession that takes place in the emanation of the trinitarian persons.^{Footnote 60} Both are called procession or emanation, but in this case the term cause is applied to the procession of created things from the divine essence in the act of creation.^{Footnote 61} In question 44, Aquinas describes God’s act of creation ex nihilo using the language of causality: for Aquinas, God is not only the first efficient cause of creation but the cause of prime matter and the exemplar and final cause of all that has being.^{Footnote 62} In this regard, Aquinas is consciously proposing his own interpretation of Aristotelian causality, which supports the Christian doctrine of creation ex nihilo and directly contradicts the Averroist interpretations of Aristotle’s natural philosophy that were being advanced by some members of the arts faculty at the University of Paris.^{Footnote 63} It is likely that the concerns generated by the Averroist crisis explain in part the caution Aquinas exhibits when discussing the divine processions in question 27. Although Aquinas does not always associate causality with the limitations of creation, in the context of question 44 the concept of “causal procession” is associated with the form of procession that describes the divine creation of material things. In this form of causal procession, although the causal origin may be divine, the causal effect exists within the temporality and contingency of creation. Because the term of this form of procession or emanation is conditioned by temporality, the procession taken as a whole with both of its terms cannot be said to exist simply or eternally.

To a certain extent, Kalekas and Aquinas are simply approaching the questions of causality and procession from the perspectives of different theological and philosophical traditions. Although it seems that Kalekas has been influenced by some of the structural and methodological aspects of question 27, he does not engage the philosophical distinction between divine and created being that Aquinas makes in this context or associate causality with the concept of creation. When understood in its proper context, it is likely that Aquinas’s cautions against causality in question 27 are primarily intended to warn against the use of certain models of causal procession in trinitarian theology that were current in Latin Aristotelianism, rather than those found in the earlier Greek patristic tradition. As will be shown, further evidence to support this supposition can be found in the wider context of Aquinas’s treatment of the Trinity in the Summa, where he goes so far as to describe a particular causal understanding of trinitarian procession that differs from those that result in Arianism and Sabellianism and that could be employed in a doctrinally orthodox way.

The Summa and the Greek Fathers: Procession as Instrumental Causality

Unlike many of his Latin contemporaries at this time, Aquinas had a strong interest in the Greek fathers, and because of the presence of Dominican missionaries in Byzantium, he also had an unprecedented degree of access to Latin translations of Greek texts and Greek-speaking Dominicans familiar with the Byzantine theological tradition.^{Footnote 64} The influence of these sources would directly impact Aquinas’s thinking on a number of subjects, including trinitarian procession. Despite his strong warning about the use of causal language in question 27, when discussing the individual trinitarian persons in the later questions of his treatise on the Trinity Aquinas shows a great deal of sensitivity toward the Greek patristic tradition. When discussing God the Father in question 33, Aquinas acknowledges that the language of causality is used among “the Greeks,” arguing that in this usage “cause” is equivalent to the Latin concept of principium.^{Footnote 65} Gilles Emery shows that this position represents a development within the thought of Aquinas from his earlier position in the Sentences, where Aquinas ruled out any use of causality in this context.^{Footnote 66} The Contra gentiles, which was completed in 1265, before Aquinas departed from Orvieto for Rome, does not engage this issue directly.^{Footnote 67} Even in later works like De potentia dei, Aquinas still expresses concern that the language of causality may say more than is appropriate about the Trinity.^{Footnote 68} We have seen Aquinas express these sentiments in question 27 of the Summa as well. However, although Aquinas still warns against an incautious use of causality in question 33, in this text he is also careful to assert that the Greeks do not mean to imply such things when they use the word “cause.”^{Footnote 69} Emery attributes this approach to Aquinas’s increasing familiarity with Latin translations of the works of Athanasius, Basil, and Gregory of Nyssa, among others.^{Footnote 70} In question 36, the influence of these Greek sources would directly affect Aquinas’s approach to trinitarian procession as well. In his discussion of the procession of the Holy Spirit in question 36, Aquinas actually provides a conceptual model for understanding causal accounts of trinitarian procession that avoids the pitfalls that are described in question 27. In this text, Aquinas argues that causality can be used to describe the procession of the Spirit through the Son. In support of this, he cites Hillary of Poitiers, who describes the Holy Spirit as being through (per) the only-begotten of the Father.^{Footnote 71} Aquinas develops this in the body of the article by using an adapted form of causal language that differs from the forms of causality that he associated with Arius and Sabellius in question 27. In question 36, Aquinas argues that it is possible to speak of the procession of the Spirit as through the Son, inasmuch as the Son has received from the Father that the Holy Spirit proceeds from Him (the Son). As in his discussion of the Father in question 33, Aquinas again equates the concept of causality in this context with the Latin language of principium. Concerning procession itself, Aquinas argues that when “cause” is understood as action through, it is not construed as a median between the acting agent and the thing done. Instead, the term through is predicated of the cause itself of the thing done, such as an artist acting through a hammer, or a king acting through a bailiff. Additionally, this sense of action through can also be predicated indirectly, as in the case of the bailiff who works through his king.^{Footnote 72} Like a hammer in relation to an artisan, the example of the bailiff and the king describes a relationship between a principal and an instrumental cause. When the causal action that proceeds from this relationship is examined, it can be understood from the perspective of either the principal or the instrumental agent. In many ways, these arguments reflect the influence of the same Cappadocian authors who influenced John Bekkos and other Byzantine unionists. For Aquinas, when causal action through is predicated both principally and instrumentally, it becomes possible to understand divine procession in the language used by both the Latin and the Greek Churches. When the language of causality is used to describe the Father and the Son, Aquinas argues that it is possible to claim with the Latin Church that the Spirit proceeds from the Father and the Son, because both are causal principles of the Spirit’s procession. Relying on the distinction between principle and instrumental causes, Aquinas argues that one may claim with the Greek Church that the Spirit’s procession is from the Father immediately, and the Son mediately, not unlike the case of the king and his bailiff. In this understanding, the Spirit’s procession can be said to be from the Father through the Son.^{Footnote 73}

The significance of this should not be underestimated. Because of this careful, twofold predication of through as a causal term, Aquinas is able to use the language of Latin theology to establish the legitimacy of a causal understanding of procession in which the Spirit proceeds from the Father through the Son as an effect from a cause: “Therefore, because the Son has from the Father that the Holy Spirit proceeds from him, it is possible to say that the Father spirates the Holy Spirit through the Son, or that the Holy Spirit proceeds from the Father through the Son, which is the same in meaning.”^{Footnote 74}

Despite his strong warnings against causality in question 27, therefore, in question 36 Aquinas clarifies this teaching, specifying which versions of causality might be used to describe the procession of the Spirit from the Father and through the Son. Although causality initially seemed to be a point of conceptual divergence between Aquinas and Kalekas, it is clear that in the Summa, Aquinas’s opposition to causality in the context of trinitarian procession is in fact restricted to certain noninstrumental forms of causality that imply created limitation. Given the prevalence of causal accounts of trinitarian procession in Byzantine theology, Kalekas would have had many reasons, independent of his interest in Aquinas, to adopt a causal account of trinitarian procession in De fide. However, a close reading of questions 33 and 36 in Aquinas’s Summa would have certainly made it clear to Kalekas that Aquinas’s warnings about causality in question 27 should not be adopted without qualification, and that Aquinas himself believed that Cappadocian accounts of trinitarian procession could be articulated in ways that were compatible with Latin theology.

After Kalekas: Subsequent Reception

In the years after Kalekas’s death in 1410 the work Kalekas and others within the Kydones circle had done to place the theological traditions of the Greek East and the Latin West in dialogue would prove important. In 1431, the Council of Basel would begin to address formally some of the points of tension between Byzantine and Latin theology, and this work would be continued by the Council of Florence (1438–1445). With both Latins and Greeks in attendance, in 1439 the Council fathers agreed that, concerning the role of the Son in the procession of the Spirit, precedent existed within the church’s tradition that justified the formulation of this procession of the Spirit as either from (ἐκ, ex) or through (διά, per) the Son, and that these different formulations asserted the same truth.^{Footnote 75} Further, the Council interpreted the Greek formulation δι᾽ υἱοῦ using the language of causality (αἰτία), arguing that the formulation of the Spirit’s procession through the Son found in the Greek fathers should be interpreted within the language of causality that is used by the Greek tradition to describe the procession of the Spirit from the Father, in such a way, of course, as not to create two principles.^{Footnote 76} In this regard, the council effectively acknowledged a doctrinal equivalence between the Greek language of cause (αἰτία) and the Latin language of principle (principium), when speaking of the trinitarian processions.^{Footnote 77} We may surmise that those texts from Aquinas’s Summa theologiae that have been examined here likely provided an important resource within Latin theology for these conclusions. From the perspective of Byzantine theology, the continued influence of the Kydones circle played an important role in reaching this doctrinal agreement. Both Theodore and Andrew Chrysoberges—members of the Kydones circle in Constantinople in the 1390s and associates of Kalekas—were part of formal conversations between the Byzantine and Latin Churches in 1415 and 1430 that served as a foundation for the union established at the council of Florence.^{Footnote 78} As an early product of the Kydones circle, De fide shows that a speculative synthesis inspired by Aquinas between Byzantine and Latin approaches to trinitarian procession was actively discussed in the Kydones circle while still in Constantinople during the 1390s—at a minimum, we may conclude that the Chrysoberges brothers were aware of De fide and other similar projects and participated in the conversations within the Kydones circle that gave rise to them.

Although the departure of Kalekas and his confreres from Constantinople and the continued pressures of the Palamite controversy may have initially prevented De fide from being read widely in the East, in later centuries this text would be well received in Orthodox Christian circles. As late as the seventeenth century, De fide was included as part of a larger collection of Byzantine works compiled in 1698 by Patriarch Dositheos of Jerusalem, titled The Book of Charity Against the Latins.^{Footnote 79} Although the inclusion of a text like De fide in an anti-Latin tract may seem somewhat ironic, by selecting De fide, Dositheos also acknowledged the status of Kalekas’s text as an authentic expression of the Byzantine theological tradition.