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.
Now, when we talk about what is truly good and what 'freedom for' means in the Catholic sense, we are referring to the freedom to choose to direct one's actions towards the fostering of one's relationship with God and towards the flourishing of the community as a whole. This outwardly focused, altruistic understanding of freedom does not preclude one's own flourishing. Rather, it affirms that as beings made in the image of God, and hence as social and relational creatures, human beings flourish with others. Our flourishing is intimately tied up with the flourishing of others. When we use our freedom in this way, we respect not only the dignity of all human beings, but come closer to realizing the kind of just, peaceful and joyful community that God wants for humanity. What is truly good, in Catholic terms, is that which God wills. How do we know what God wills? Through revelation and through the use of our human reason to understand the order of the universe the way God has made it so that we can cooperate with God in making judgements and choices. Using these two sources of revelation and reason, we have already seen how we can affirm the good of every human being, their human dignity. We have seen how we can affirm the good of the body and the positive value of human sexuality expressed through procreation and conjugal love. We have seen how we can affirm the good of love, of intimacy, of being free of shame and of living whole-heartedly in a community of love, peace and justice with others. Thus, when it comes to moral reasoning about human sexuality and relationships, being able to answer basic questions about what is truly good means that our consciences are already well-informed about the starting point of our moral reflection. We come to understand such questions have answers both on the authority of God and the evidence of our own critical thought, reflection and feelings. What is said above constitutes the focus for what we should ultimately wish to achieve in all our moral decisions and use our freedom to work towards through our moral-decision making. What is discussed here provides a framework for helping us to think through what the right thing to do is in any given moral situation, especially in the context of human sexuality and relationships.