This study constructs a social theology from a theological understanding of the communio sanctorum, which contributes to the development of Christian Humanism. It is based on the unity of humankind and is sacramentally grounded in the oneness of creation. The theological basis of Christian Humanism is that there is but one God, one universe, one creation, and that all people constitute God’s one human family. The thesis is interested in Catholic thought on the subject while acknowledging that there is plenty of non-Catholic scholarship by figures such as Karl Barth, Albert Schweitzer, and NT Wright. The expression communio sanctorum (communion of saints) first appeared in Jerome’s Creed (Jerome’s Symbol, c. 370-378 CE). Jerome also in his Epistulae (92.3) denied the dissident Bishop Isidore participation in the communio sanctorum. This meant the celebration of the Eucharist. Niceta of Remesiana (c. 335-414 CE) was the first to explain the concept of “communion of saints”, which became an article of faith in his local creed alike in Jerome’s Symbol. By the time it was incorporated into the Apostles’ Creed in the late eighth century, it had acquired a personalized meaning for the Saints and their intercessory powers. This thesis will understand the phrase as a reference to the sacraments while acknowledging that the expression has been understood differently in the life of the Church. Supported by historical data, this thesis proposes a reversion to its sacramental meaning both for its theological significance and its contemporary significance from any other interpretations. The doctrine of communio sanctorum incorporates the social theology of the sacraments of Baptism and the Eucharist that distinguishes believers as authentic witnesses of Christ. Jesus taught his disciples: ‘You shall love the Lord your God with all your heart, and with all your soul, and with all your mind and with all your strength. The second is this: You shall love your neighbour as yourself. There is no commandment greater than these’ (Mk 12: 30-31, Mt 22:36-40). This study explores how communio sanctorum systematizes Jesus’ teaching becomes a life experience in today’s world. It equips believers with a range of practical strategies that creates perceptible social outcomes, as believers become more configured to a life of Christ. It internalizes the virtues exemplified by Jesus Christ’s relations with others and openness of the presence of God. The thesis will claim that the doctrine provides a cultural pattern for humanity in how Christians respond to God’s self-giving love, manifested especially via the incarnation, cruciformity, and God’s trinitarian nature as a social being. III In Catholic Christianity, the Church is the body of Christ (1Cor 12:27). It encourages a life of a community united like the children of one God. Christians constitute the Church and as the people of God, the communio sanctorum is the prototype for global, shared unity. Thus, communio sanctorum is the platform for developing a human society, which is founded on love. This understanding of the communio sanctorum contributes to a social theology of the relationship between faith and society that outweighs any appeal to individualism, indifference, and consumer-driven poverty in a rapidly changing global economy. This ought to be the basis of Christianity. Humanism, derived from ‘one God, one universe and one humanity’ whereby all human beings are as one in God’s own family. Doctrinally it was conceived to restore this fellowship of a genuine community as opposed to alienation, divisiveness, selfishness, discrimination, war, and poverty, all of which are the consequences of the fall of humankind into sin. The theology of the communio sanctorum distinguishes between the City of man (a collective based upon self-love) and the City of God (a collective founded on the shared love of God). The mission of the communio sanctorum is to restore God’s kingdom in a broken world. The social paradigm of this Eucharistic communio is that of a holistic approach to living as an authentic community. First, the thesis will argue that this communion transforms believers to imagine God’s nature by bringing love where there is hatred, forgiveness where there is resentment, and compassion where there is animosity. Second, the communio refashions the social, economic, and political realms of a broken world, aiming to achieve God’s reign on earth and leading to the development of a commonwealth characterized by human dignity, solidarity, and the common good. These are the pillars of justice for the children of God. The doctrine is the vehicle of love for one another in the Christian understanding of creation.