The trinity, as the most prominent distinctive theological doctrine of Christianity, is often defined as the belief system that the one God has three consubstantial persons or hypostases: the Father, the Son, and the Holy Spirit. In another way of saying it: Trinity means one God in three persons that are distinct yet are one substance or essence: the Father is not the same person as the Son, who is not the same person as the Holy Spirit, who is not the same person as the Father; yet the three are co-equal, co-eternal and cosubstantial; and each is God, whole and entire. Each is fully divine, yet there are not three gods, but one God; there are three individual subsistences (meaning, something that has a real existence) or persons (denoting individuality, self-awareness, and, more importantly personal qualities such as thinking [1 Cor. 2:11], loving [2 Cor. 13:14], and willing [1 Thess. 5:18]). These are the traditional way of explaining the Trinity; and it is undoubtedly confusing so that such a concept is difficult to grasp and to be explained to those who do not believe it, and even it is incomprehensible; however, Christians would respond to that by saying that incomprehensibility of God must be and is His ‘nature’ of being a mystery, which is beyond everything.
Let me begin with the incomprehensibility of the Trinity. As many critics attacking the Christian Trinity have often said, it is irrational to believe that one is three or three is one; or, that one plus one plus one equals one (1 + 1 + 1 = 1). This numerical analogy, in a sense, is not exxagerating or reducing as Christians say that God is three persons and each is different, yet equally divine, and yet they are numerically one. By different, the three persons, which are distinct one from another, are emphasized. By equally, Christians emphasize on that there is no subordination among the three (Indeed, apparently there is a kind of subordination in the Trinity: it seems that the Father is first, the Son is second, and the Holy Spirit is third; the Father is not begotten, but the Son is [John 3:16]; the Holy Spirit proceeds from the Father [John 3:16]; the Father creates [Isaiah 44:24], the Son redeems [Gal. 3:13], and the Holy Spirit sanctifies [Rom. 15:16]; but still, Christians would say that this apparent subordination of order does not mean that each of the members of the Godhead are not equally divine). By one, Christians emphasize that the triune God is inseparable one from another—because if the three are separable, it is no longer trinity, but tritheism. Despite the basis that God is three persons, God is numerically one: three in one. And to avoid partiality lies the idea that each of the three persons is completely divine in nature though each is not the totality of the Godhead; each of the three persons is not the other two persons, yet each is related to the other two but are distinct from them.
Those all are confusing and difficult to grasp, right? If so, you share the same feeling with me. Above all, to say that they are the same (equally divine and one) and at the same time different (three persons) is just irrational as it is illogical that the two opposite things (different vs equally the same) can be in one thing at the same time: one is not three must be and is as day is not night. With regard to this, some medieval Muslim scholars raised criticism by saying that “the Trinity is not a matter simply beyond reason; it is clearly opposed to reason” (Hoover, p. 4).
Another objection toward the Trinity that may come up is that such a concept is primarily derived from the scripture, the Bible. Indeed, the word “trinity” does not appear in the Bible, but Christians insist that the concept is taught there (This is the same as that the word “bible” is not found in the Bible, so are such God’s attributes as “omniscience”, “omnipotence”, and “omnipresence”, yet this does not meant that such concepts are not taught in the Bible). Among the biblical bases of the Trinity is John 1: “In the beginning was the Word, and the Word was with God, and the Word was God; He was with God in the beginning… The Word became flesh and made his dwelling among us.” Another passage is Matt 28:19: “Go therefore and make disciples of all the nations, baptizing them in the name of the Father and the Son and the Holy Spirit” (other passages: 1 Cor. 12:4-6; 2 Cor. 13:14; Eph. 4:4-7; 1 Pet. 1:2; etc.).
My point on that is, it is apparent that the Trinity is conceptualized conforming with what the scripture has described about who God is; not the reverse. In other words, in order for one to believe in the Trinity, one must first believe in the fact that the Bible is divinely inspired; it is the scripture first, then emerges the belief system called Trinity. To put it bluntly, the Trinity is an interpretation of the Bible’s God. Besides, Jesus never claimed to be God worth ‘worshiping’; Jesus never said “I am God and you all must worship me!” Such a claim is not found even in the Bible (Note: this type of criticism is often raised by Muslims, brought about by comparing the biblical Jesus with their Quranic idea of who God should be).
No less important, recent scholarships tracing the history of early Christianity, including the so-called “quest” for historical Jesus, have come up with some critical conclusions to the Christian belief system. Among them is that the idea of Trinity, particularly in the idea of Jesus as God’s Word, is derived from Hellenism: it was Philo who was known for “clothing the stories of Jewish scriptures in Platonic terms and speaking of the Logos, the ‘Word’, as the mediating principle between divine transcendence and materiality” (Levine, p. 21).
Another criticism says that it was actually Paul who was inventing Christianity by elevating the human Jesus into a Hellenistic myth about a dying and rising god, a myth that was then formalized in the doctrine of the Trinity adopted by the Council of Nicea. In this regard, Paul’s assertions of Jesus’ divine sonship was “derived from pagan ideas of divine sonship and were intended primarily to legitimate Jesus as object of worship to Paul’s pagan converts in terms that they could readily appreciate from their pre-Christian religius background” (Hurtado, p. 191).
That is it. Those three things (irrationality, the presupposed belief in the Bible, and the historical cricitism) are among the key arguments that are often used to ‘destroy’ the Christian foundational faith about God. In responding to this, Christians must of course challenge them; and among the key sort-of apologies that Christians bring up is that because God is beyond everything He has created, He and His actions and attributes must not be comprehensible by His creation’s understanding, and He is basically ineffable. Among the consequences of this incomprehensibility is that the three persons cannot be “added up as numbers as they underlined the indivisibility, simplicity, and incomprehensibility of God’s essence” (Hoover, p. 3). God’s ineffability and essential mystery (and the Trinity, to the most extent, is a mystery) is in the extent to which a completely comprehensible and humanly understandable explanation of God’s essence and nature is not possible. In fact, the fourth-century Cappadocian theologians have long said that “Trinitarian doctrinal statements must be made and interpreted from within the prior framework of God’s simplicity and ineffability” (Hoover, p. 3). In this framework of ineffability, God is incomprehensible in the extent to which it is possible, as Barth argues, that “the one God in his lordship is free to differentiate Himself from Himself, to become unlike Himself and yet to remain the same” (Hoover, p. 11). In short, through this perspective of God’s incomprehensibility and mystery, the existence of the triune God is just possible.
How, then, to speak about God since He is ineffable? The only possible way is through “analogy”; yet the technical term of the “theological language corresponds to God in himself in certain oblique and ambiguous ways, not in all respects” (Hoover, p. 10). The idea that the Son is equal to the Father in his divinity but inferior in his humanity is sometimes analogized with a wife who is to be subject to her husband but the two are the same essence as to humanity. Or, as compared to Islamic theology, “the Christian problem of how to speak of the three as one and the ones as three is akin to the Islamic theological problem of conceiving the unity of the many divine attributes in al-tawhid al-sifati” (Hoover, p. 10). In fact, both Muslims and Christians believe that there is only one God who is fundamentally simple, mysterious, and incomprehensible. This God creates the world, seeks to communicate with humankind, and desires a human response of undivided worship and service: “God’s communication and interaction with humankind has taken place most decisively in Jesus Christ for Christians and in the Qur’an for Muslims” (Hoover, p. 13). While in Islam, God does not directly interact with humans and His inspiration is mediated by angels (thus, Islam has an emphasis on divine transcendence), Christians believe that it is possible for God to become flesh and directly interract with humankind on earth in history. Indeed, the Christian Trinity emphasizes on divine immanence.
Hoover, Jon. “Islamic Monotheism and the Trinity”, Conrad Grebel Review (2009).
Hurtado, L.W. “Paul’s Christology”, The Cambridge Companion to St Paul.
Levine, Amy Jill. “Introduction”, The Historical Jesus in Context.