My point is that a knowledge of God in, through, and as Jesus Christ leads to a Trinitarian way of thinking about God; and a Trinitarian theology is inherently a practical theology in that it is a knowledge of God’s action grounded in God’s being. The doctrine of the Trinity is the basis for Christian practical theology.
Practical theology is theology that is concerned with action: first, with God’s mission, the mission Dei; and second, with the action or praxis of the church in its life and ministry in faithful communion with the God who acts, the mission of the church. But God’s acts are always first, and our acts, the church’s acts, are always second, and even then, I argue, our acts are but a participation in the Holy Spirit in our Lord’s human response on our behalf to the prior act of God. Even in response we find ourselves within the sphere of God’s prevenient grace and the functioning of the Holy Trinity…
As a broad and inclusive category, practical theology is theology that is concerned with action. Yet the meaning of the term is not obviously cogent, combining as it does the noun theology with the adjective practical. Is not theology associated with ideas and arguments that seek to present eternal truths, while the practical tends to be associated with the mundane, ‘where the rubber hits the road’? The adjective seems to qualify the noun in an odd way. It is precisely this way of thinking, however, that has led theology to be thought of as ‘pure’ and therefore impractical, and ‘practical theology’ to be thought of as the functional, pragmatic end of the curriculum, where the theory of theology gets applied in churchly work. Even if, with Schleiermacher, we think of practical theology as the crown of the theological enterprise, it remains a discipline struggling to develop a theory.
So, in what way does it make sense to speak of practical theology? Practical theology is practical because it is theological: it has to do with God. All theology, all knowledge of God, by virtue of the subject matter – the acting God – is inherently a practical theology or a practical knowledge of God. Axiomatically, knowledge of God is knowledge of God creatively, redemptively, and eschatologically active in the world and in human history through Jesus Christ. Aside from the specific history of revelation and redemption, we would not know God. Knowledge of God is knowledge of the missio Dei, of Jesus’ ministry to the glory of the Father, in the power of the Holy Spirit, for the sake of the world. Revelation and the mission of God for reconciliation are held together christologically for the church as practical knowing: ‘All things have been handed over to me by my Father; and no one knows who the Son is except the Father, or who the Father is except the Son and anyone to whom the Son chooses to reveal him’ (Luke 10:22)… Because there is no knowledge of a God absent from history, or of an uninvolved God, there is no such thing as impractical theology, which would be the knowledge of a God notable exactly as a God who is not revealed and who does not act in human history… It is not we by our actions who make theology practical (the old notion of practical theology as applied theology), but it is God, by virtue of what God does, who makes knowledge of God inherently a practical knowledge. This means that churchly practice arises out of our sharing in the practice of God, and it is only properly and appropriately practical insofar as it does this. Nothing could be more practical than the teaching about who God is and what God does in relation to us, on the one hand, and the concern to live in that relationship as the fundamental or constitutive basis of what it means to be a human being and the church, on the other.
From Andrew Purves, Reconstructing Pastoral Theology: A Christological Foundation (Louisville: Westminster John Knox, 2004), xxv, 8-10 (italics belong to the author; bold belongs to me)