Human beings are capable of doing the right thing because God is just. God's rational nature is important for another reason: it means that God is not unfaithful to God's promises. If God were unreliable and capricious human beings could never know what was true and what was not, what was good and what was bad, what was right and what was wrong. Because God is rational God has created a rationally ordered universe. God has gifted human beings with the capacity to reason and to gain insight into the rational order. Christians are therefore able to believe that there is a truth in any given situation and that truth is accessible, at least in part, to human beings through the use of their reason. God can be trusted to honour the promises made to human beings. Human beings, as images of God are called to be just, ensuring that God's deepest desires for humankind and the world are realized.
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.
The link between this conception of love and with the notion of 'preference' helps us to see another important dimension of the Catholic understanding of love. Love is intimately interwoven with justice. With this in mind scholars have discussed and debated the precise nature of the love-justice relationship for many years. What is clear from all of these debates is that irrespective of whether love is prior to justice or justice is prior to love, or whether justice is a kind of love or love is a kind of justice, the two are inseparable. To truly speak of justice, one must talk of love and to truly speak of love, one must talk of justice. Justice without love is hard and calculating. Love without justice can become self-absorbed and unfocused. So when Catholic social teaching talks about a 'preferential option for the poor' it is talking about loving by doing justice and about doing justice with and for love. So too, in the context of interpersonal relationships, to love someone, to truly 'prefer' someone, is to make sure that all of your interactions are truly just. What is sought is the mutual good of both parties not simply one's own good. Mutual love also extends outwards to the wider community.