Conclusion
We have seen that exploring one central ontological question—the question whether there is a God—leads you into the heart of metaphysics. You must think about necessity and possibility, about the nature of existence, about free will.
You are drawn into questions in logic and epistemology, in ethics and the philosophy of science. Metaphysics impinges on other areas of philosophy; every area of philosophy has its metaphysical dimensions.In the early part of the twentieth century, metaphysics fell into disrepute because the logical positivists argued that metaphysical questions, since they could not be settled by logic or scientific method, were vacuous, empty of content. The verification principle, which we discussed in chapter two, requires that metaphysical questions should be decided on the basis of evidence, if they are to be regarded as being real questions. I have tried to show in this chapter that both argument and evidence can play a central role in metaphysical discussion, so that the positivists were wrong. That is why metaphysical debate, which began centuries before Aristotle, is still going strong.