The multiverse hypothesis is the leading alternative to the competing fine-tuning hypothesis. The multiverse dispels many aspects of the fine-tuning argument by suggesting that there are different initial conditions in each universe, varying constants of physics, and the laws of nature lose their known arbitrary values; thus, making the previous single-universe argument from fine-tuning incredibly weak. There are four options for why a fine-tuning is either unnecessary to invoke or illusory if the multiverse hypothesis is used as an alternative explanans. Fine-tuning might be (1) illusory if life could adapt to very different conditions or if values of constants could compensate each other. Additionally, (2) it might be a result of chance or (3) it might be nonexistent because nature could not have been otherwise. With hopes of discovering a fundamental theory of everything all states of affairs in nature may perhaps be tautologous. Finally, (4) it may be a product of cosmic Darwinism, or cosmic natural selection, making the measured values quite likely within a multiverse of many different values. In this paper I contend that multiverse scenarios are insufficient in accounting for the fine-tuning of the laws of nature and that physicists and cosmologists must either accept it as a metaphysical brute fact or seriously entertain the hypothesis of a fine-tuner.
I. Outlining the Multiverse Hierarchy
Contemporary physics seem to indicate that there are good reasons, theoretically and physically, for the postulation a plurality of worlds. This concept has come to be understood as the multiverse. The multiverse is not monolithic, but it is modeled after the contemporary understanding of an inflationary model of the beginning of this universe. Max Tegmark has championed the field of precision cosmology and has proposed the most prominent versions of the multiverse. Tegmark has made a four-way distinction in classifying these models.