A long one today:
The knowledge of revelation, directly or indirectly, is knowledge of God, and therefore analogous or symbolic. The nature of this kind of knowing is dependent on the nature of the relation between God and the world and can be discussed only in the context of the doctrine of God. But two possible misunderstandings must be mentioned and removed. If the knowledge of revelation is called "analogous," this certainly refers to the classical doctrine of the analogia entis between the finite and the infinite. Without such an analogy nothing could be said about God. But the analogia entis is in no way able to create a natural theology. It is not a method of discovering truth about God; it is the form in which every knowledge of revelation must be expressed. In this sense analogia entis, like "religous symbol", points to the necessity od using material taken from finite reality in order to give content to the cognitive function of revelation. ... The phrase "only a symbol" should be avoided, because nonanalogous or nonsymbolic knowledge of God has less truth than analogous of symbolic knowledge. The use of finite materials in their ordinary sense for the knowledge of revelation destroys the meaning of revelation and deprives God of his divinity.
Systematic Theology I, 131.
This immensily important realisation, that talk about God must be symbolical in order to protect the truth about God, in one stroke makes fundamentalist and traditionalist theology impossible. This is why theology, to be theology, must change. I cannot remain the same, it cannot use the same formulas and concepts as before because human language is constantly in flux. In that situation, to hold on to traditional formulas in theology, without trying to explain them with current language will lead to lying about God.
Of course, it is this realisation that leads Tilich to develop theology with the "method of correlation", as an attempt to find new form to the eternal truth contained in the Christian gospel.
I have had great use of this method not only in my few and far between sermons, but espeically in my reading of Christian litterature, especially in my case the fathers. To always keep the "existential question" they are trying to answer in the back of my head while reading has helped me, I think, to appreciate an aspect about the fathers that go beyond theological polemics, the main trap of any reader of patristic literature.
Clearly this is not an uncomplicated matter, for it leads over to the very tricky question of what remains the same and what changes in the human condition over the ages.