Human beings are relational because God is relational. The theological mystery of the Holy Trinity claims that God is one being, but three persons. The person of God whom the Tradition calls Father is the Creator, the source all things. The Father has spoken the eternal Word (the Son) into creation, and through the incarnation, Jesus of Nazareth is the visible expression of the Father. The Spirit is the active presence of God bringing creation to its ultimate destiny which is eternal life. These three persons of God co-exist eternally in a state of mutual indwelling, a very deep interpersonal relationship of boundless love (See section on Trinity in Part III).
Human beings are able to love because God is love. Believing that God is free, rational, just and relational is helpful in explaining many human experiences and the way the world works. But this belief about God is not particularly helpful in answering the question of why God created the world, human beings, the human individual. The Christian tradition believes that God is Love (1 John 4:8). God creates the world, every creature and every human being out of this perfect love. Unlike other creatures, human beings, as images of God, are both loved and are capable of love. Human persons are capable of knowing and loving themselves and, more importantly, they are capable of knowing and loving others with a profound intensity. It is this deep love, this deep gift of self, that Christian's believe triumphs over even the greatest trials, even death.
Love is the basic vocation we all share. We begin with love, continue in love, and reach our fulfilment of love through, with, and in God when we die. The desire to be loved and to love, to be united with one another, is a deep-seated and natural yearning flowing from being created in Love's own image. God, whose Trinitarian being is to-be-in-relationship, invites us to a 'destiny of union with God and other(s) in self-giving love' (Coultier & Mattison III, 2010 p. 211)
The Christian understanding of God is a Trinitarian one. All relationships are meant to mirror the relationality that constitutes the Trinity. All relationships are to be characterised by love, radical equality, mutuality, inclusivity and justice with mercy. God is a Trinity of Father, Son and Holy Spirit. This is not to say that there are three Gods. Rather this mystery gives expression to three 'persons' of the same divine being (substance). Three persons in one God. Christian mystics have contemplated this mystery for centuries. The central aspect of most of these reflections is how the idea of the Trinity helps us to understand what it means to say that God is love. The persons of the Father should not be understood to mean that God is male since God has no gender (CCC 370). God the Son or the Word becomes incarnate as a human being, Jesus of Nazareth. Together with the Spirit all three persons are necessary if God is not to be reduced to simply an unmoved mover, or some omnipotent power. These three persons make God understood as pure divinity, the greatest good, the most powerful power, fundamentally relational and personal. Moreover, God's fundamental relationality is defined not by power or violence or competition, but by love. This means that contrary to many other conceptions of divinity or of gods such as Deistic notions of God as divine clockmaker, the Christian conception of God makes relationship with the world and with human beings, and a genuine concern for the wellbeing and flourishing of the world and of human beings, fundamental aspects of God's very own existence. We say, therefore, that the Christian God is a personal God, who is actively engaged in and with human beings and their affairs in history. God cares. God must care. It is part of God's very nature. It is worth unpacking this notion of Trinity a little further because it helps to explain what it means to love, to 'see as God sees', to prefer as God prefers. The relationship is as follows. The Father begets the Son, and the Spirit proceeds from the Father and the Son. The relationship between the Father and the Son can be thought of as the relationship between the giver and the receiver of love and the reciprocation of the giver's love by the receiver. Out of love, the Son is begotten by the Father. The Son, in return, looks back with love to the Father. This mutual gaze of the Father and the Son, the giving and receiving of love, gives rise to the Spirit, a love that expands beyond the two into a genuine community of love. We can expand this understanding of relationality within God to explain the relationship between God and human beings. Just as the Father loves the Son, so God loves each and every human being. The Son reciprocates that love for the Father and so each human being is called by God to return God's love. This entails accepting with gratitude the gift of existence. It involves the realization that each individual is uniquely willed and loved by God. Finally, just as the Spirit flows forth from the love between the Father and the Son forming a Trinitarian Communion, so my love for my neighbour, my spouse, and my children, flow forth from God's love for me and my love for God forming a community of God, self and other. If I accept that God loves me, then I must also realise that God loves each individual. So when I see as God sees, when I love in the Christian sense of the word, I prefer the other person in the way that makes real God's preference for that person, a preference that God has for every human being. So to say that a Christian understanding of love is to 'see as God sees' is to say that in the other person I recognize someone who is like I am, but is not me. Nor is that person a product or an object of my creation or of my willing. Rather, that person is always an Other, a unique image of God, willed by God for his or her own sake. That person is loved by God. God's desire is for that person to share in the eternal love that is part of the communion of the Trinity.