I have been reading about Aquinas, Calvin, Schleiermacher, Barth, Tillich, and Pannenberg at seminary for some years. One interesting question I had (like many other students) was regarding some of the differences and similarities between the prolegomena of these theologians. For this reason I will try to respond to this question in a few sentences hoping it can be useful for those interested in the topic.
For Aquinas, God reveals himself in both Scripture (through special/divine revelation) and in nature (through general/natural revelation). Aquinas follows Paul’s words in arguing that the impious might have natural revelation through the senses of the creation order. This natural revelation, however, cannot be comparable to divine revelation, which it is superior. In this way Aquinas links reason to the natural order and sacred teaching to the divine order. Thus, the role of natural knowledge offers us some glimpses about God but nothing of his saving work. Despite this, Aquinas does not dichotomize nature vs. grace. Divine revelation completes what the natural knowledge cannot do. As one observes, Aquinas’s understanding of knowledge of God (natural: reason/revelation: faith) is twofold. This means, for Aquinas both are different but related to each other. Based on this, it is not a surprise Aquinas understood theology as science. That is, theology belongs to both the public sphere and the sacred sphere. All truth is God’s truth so any truth discovered by natural sciences does not mean it is automatically in disagreement with the faith.
For Calvin, the knowledge about God is not something human beings need to discover but to receive. What God has revealed to humanity has been made us known through two different yet related means: general and special revelation. General revelation is appreciated when we consider the creation and its divine preservation. This teaches people about God’s power and how insignificant we are. Despite the importance of general revelation, God makes himself known to us more clearly by his Word. This special revelation leads to Christ’s salvific work. Since revelation belongs to God, Calvin distinguishes between natural instinct v. God’s self-revelation. As he highlights, natural instinct is an awareness of divinity. The purpose of this natural instinct is to make known all humanity that there is a God and that this God has created them. Thus throughout his works, God has revealed his existence and glory to humanity. Since this natural instinct is intended for all people, then it has a broad purpose: making God known to humanity. The other way God himself reveals to humanity is through special revelation in the Scriptures where we are told what the natural instinct cannot. Following Psalm 19 Calvin recognizes that the creation does not say all there is to say about God but it is an starting point. Due to the sinful nature of the human soul, all people need revelation in order to understand what God wants them to know about his character, essence, and plans for his people, including the plan of salvation and redemption through Christ.
For Schleiermacher, God does not speak through the natural and/or spiritual world, but instead through historical events. His redefinition of faith as the dependance ‘feeling’ on God makes him give religious experience a great degree of authoritative power. This is so because revelation, for Schleiermacher, is a matter of human affairs. Even Christian doctrines does not depend on the Scriptures but on the formation of the Christian experience. One observes that what tries to do Schleiermacher is saving religion from becoming a dry exposition of dogmatic and rational arguments. Despite his critique to rationalism, Schleiermacher still believed that theology/religion has a ‘scientific’ character. For him, religion constitutes the foundation for the sciences and thus, it is related to all areas of human knowledge.
For Barth, Jesus Christ constitutes God’s self-revelation, so that God speaks to humanity through Christ. Therefore, God is then the author for theology and all theological language must be found only in him. With this view, Barth places the main responsibility of speaking about God to the church. This is so because in Barth’s view theology is always confessional. Theology, for him, is about propositions focusing on the knowledge of /to God. As Barth asserts, out of revelation there is no saving knowledge, making thus natural knowledge impossible. With this state of affairs, Barth even consider it is an oxymoron speaking of ‘Christian philosophy’ because both are incompatible and opposed each other. In brief, Barth sees a contradiction mixing theology with philosophy other natural sciences since he locates theology only in God (no room for theology as science!). For Barth, nature and of grace dialectically oppose each other.
For Tillich, the notion of God is a panentheistic so God is beyond all essence and existence. So speaking of God would be only a nonsense in the literal sense. The object of theology for Tillich is what concerns people in the moment of questioning their ultimate concern. It could be before death or a life crisis. At that time, a person’s propositions are regarded as theological because it becomes related to his/her ultimate concern. The importance of the notion of the ultimate concern is that it defines a person’s being/not-being. Depending on people’s concerns, they will be grounded on either one. Therefore Tillich links the tasks of theology to the process of questioning the ultimate concern. When this happens theological discourse emerges and God can speak through the discourse where the person with the ultimate concern speaks with the theologian. There the Christian faith correlates with the person’s ultimate concern.
For Pannenberg, because of his apologetic nature in his discussions in general, his audience seems to be focused on the non-believer intellectual persons. For him theology has an universal concern and not only concerns the church. A significant feature of Pannenberg’s theology is his understanding of revelation as history. This makes important questions emerge: Does God reveal himself in some way in some part… And if so, how? For Pannenberg, the only part we might find divine self disclosure is in the gospels and/or New Testament. However, one must remain cautious because for Pannenberg, those disclosures are not true but are alien notions introduced by the Greeks. It seems there is no room for God’s self disclosures at all in Pannenberg’s theological program. He tries to fix the issue introducing an indirect method: God reveals himself through historical events. Despite this, humanity cannot have a complete picture of who God is. Each historical event is not complete in itself but it forms part of a bigger picture: it is in the final resurrection, when Christ returns and the kingdom of God becomes realized completely, that people will be able to have a complete yet indirect revelation of God. Put it in simple word: Christ is the end of human history.
Although modern scholarship such as Muller and Vos argue that Calvin was not very aware of Aquinas’s theology, Calvin’s twofold notion of the knowledge of God, and his affinity to natural theology resembles a little bit to Aquinas. Respecting to Muller and Vos’s conclusions, it seems that Calvin perhaps acquired some Thomistic basic thoughts indirectly via others theologians of his times. Of course, Calvin allows natural theology but in a limited way. As Horton argued, for Calvin his allowance of natural theology in his theological thought is shaped not by philosophy but his pastoral concerns. At the end, for Calvin out of Church there is no forgiveness of sins or salvation. Pannenberg and Schleiermacher seems to have opposite goals in their theological agendas, a common ground is appreciated when they both understand revelation as historical events. Definitively, both rely on the tradition of German Idealism for their understanding of history. And speaking of tradition, Calvin, Schleiermacher, and Barth shared a common theological tradition: the Reformed faith. Even Calvin, Schleiermacher, Barth shares significant common aspects in their theology, it must be noted Barth’s rejection of Schleiermacher’s notion of God and Barth’s reinterpretation of Calvin. Overall, despite their differences, we might locate in a single place to Calvin, Schleiermacher, Barth for their emphasis on the kerygmatic character of their discourse (using the term in a broad sense). This could be in contrast, at least in limited ways, with Aquinas and Pannenberg who tend to emphasize the apologetic dimension of the proclamation of the gospels. The case of Tillich is unique. He tries to different between both sides, the apologetic and kerygmatic. Indeed he was successful in this task.
As observed, the similarities and differences of these theologians in their understanding of what theology is and what is its audience mark a clear path for readers to know from what perspectives they are doing theology. Those aspects also help us to better understand the continuities and discontinuities of these theologians in respect to their forerunners, context, and tradition.