Newbigin concludes chapter 4 with five propositions which serves as the launch point for the crescendo that is the final two chapters.
- While the methodological elimination of final causes from the study of nature has been immensely fruitful, the attempt to explain all that exists solely in terms of efficient cause leads to conceptual absurdity and to social tyranny.
- To recognize the place of final causes in the understanding of the world must lead to these questions: Is anyone there? Is there a word? This is because purpose is a personal reality and can be known only if the person whose purpose it is chooses to communicate it.
- The church exists to testify that there is someone, that he has spoken, and that we can begin to know his purpose and to direct our personal and public lives by it.
- The church, therefore, in its missionary encounter with modern Western culture, has to be quite bold and unembarrassed in using the language of testimony, since this testimony, so far from being capable of validation by methods of modern science, provides itself with the foundation on which modern science rests, namely, the assurance that the world is both rational and contingent.
- When the ultimate explanation of things is found in the creating, sustaining, judging, and redeeming work of a personal God, then science can be the servant of humanity, not its master. It is only this testimony that can save our culture from dissolving into the irrational fanaticism that is the child of total skepticism. It will perhaps be the greatest task of the church in the twenty-first century to be the bastion of rationality in a world of unreason. But for that, Christians will have to learn that conversion is a matter not only of the heart and the will but also of the mind.