For those who find it difficult to maintain that free will is the greatest possible good there are still several possible alternatives that could yield the existence of a multiverse. In the first alternative, it seems that we can substitute something such as happiness, joy, or pleasure for free will, and the multiverse account may still remain the same. Surely we can agree that there are different types of happiness, and failing that; there are at least different ways of attaining happiness.14 This being the case there would seem to be different kinds of happiness that are incompatible with each other, such as the happiness or satisfaction felt from eating the last piece of your favorite cake immediately, and the happiness or satisfaction felt from saving that same piece of your favorite cake for later and enjoying it after a period of anticipation. Assuming that the situations that we are talking about both involve the exact same person and the exact same piece of cake then it seems that enjoying both of these kinds of happiness is not possible since one cannot both be happy that he is currently enjoying the last piece of his favorite cake while simultaneously enjoying the anticipation of being able to enjoy his favorite piece of cake at a later time. Returning to the previous terminology of “units of good,” with each kind of happiness equating to one unit of good, then, in this case, only one unit of good could be recognized while the other is left as potential. In order to recognize both units of good and create a maximally good world (or multiverse), a second universe would be needed so that both kinds of happiness can be instantiated.
The same principle follows for a wide range of other goods such as for example, justice, existence, life, and so on. For each different good, it seems that within it there are multiple variations of that good that may not be compatible with each other, thus requiring a multiverse in order to realize all of them. While I will not go on into such detail as to provide examples, as I have done with free will and happiness, it stands that such an account is at least plausible and that for any good that is argued to be the greatest possible good a multiverse will be entailed by it.
Secondly, for those who do not want to maintain that there is a single greatest possible good, rather that there are a variety of inherent goods that are on-par with one another or that there is a greater goodness held in a variety of goods rather than a flood of one greatest possible good, this too could entail a multiverse. In this case, it is not altogether clear that there is a single instantiation of a variety of goods is any better than any other instantiation, and given the principle of plenitude, it still seems that God would create a multiverse in order to realize all possible combinations of goods. For example, it is not clear that a universe, universe A, whose maximal goodness is composed of 50 percent happiness, 30 percent justice and 20 percent free will is any better than another universe, universe B, whose maximal goodness is composed of 40 percent life, 25 percent pleasure and 35 percent honesty. Whether universe A is better than universe B or not, it seems that God would be obliged to create both of these universes, and a whole host more, since they are all on-balance good, and more of a good thing is a better thing. The universes that God would create would be ones that exhaust every possible composition of every inherent good that yields an on-balance good universe, thus resulting in a maximally good multiverse. Again, while the individual universes themselves will not yield maximal goodness, they comprise a multiverse that is maximally good.
The Scientific Case for the Multiverse
As with the case in philosophy, much work is going on in the sciences (primarily physics, for our purposes) regarding multiverse theories. Tim Wilkinson notes that “[a]t the coal force of science . . . it is usually extra-ordinarily difficult to find even one theory that fits the facts. In the current context, we do have a few competing theories, but all imply broadly the same thing: a multiverse” (2013, p. 94), meaning that while a survey of the literature seems to suggest that there is scientific consensus on the existence of a multiverse the debate arises in just what kind of multiverse we happen to be a part of. For the scientific community, according to Wilkinson, the question is not whether a multiverse exists, rather there are questions about the composition of the multiverse, the origins, the physical constants of the multiverse and the individual universes within it, and so on. Similar to the previous section and the treatment of philosophical discussions of the multiverse the following is a short introduction to several ideas within physics regarding the multiverse.15 While I do not generally go into detail regarding the methodology and justification for the various multiverse accounts presented (since they are typically quite complex and laden with mathematical jargon) I present the concluding prediction of each theory. The reason for including a section on the scientific perspectives of the multiverse, in this overall philosophical discussion, is twofold. In the first case, scientific approaches to the multiverse provide us with just that, a different approach, bringing to light different conceptions of the composition, formation, and general structure and nature of the multiverse. The second reason is that, while philosophical approaches to the multiverse may be logically consistent and conceivable, scientific approaches seem to have that extra level of justification given that they have to be not only logically consistent but physically plausible as well. That is to say; I think that any philosophical view of the multiverse, no matter how strong it may be, can be strengthened and given more credibility if it is supported by a scientific account of the multiverse.
Max Tegmark composed a paper that serves as somewhat of a survey paper, not of particular scientific theories of the multiverse, but of the different and more general types of multiverse theories available within physics (Tegmark, 2007). Tegmark argues that most (if not all) current scientific multiverse theories taken seriously propose or predict multiverses that fit into one of four distinct categories, or levels, as he calls them. Each level, beginning with level 1, progressively varies more and more (with regards to the physical constants, laws of nature, etc.) from our universe. Similarly, as the levels progress up from 1 to 4 the multiverse theories that fall under them become increasingly debated and less easily accepted. That is to say, level one is the multiverse model that contains individual universes that are most similar to ours, and is also the multiverse model that garners the fewest objections and sparks the least debate within the scientific community whereas the level 4 multiverse is the model that contains individual universes that vary significantly from ours and is also the multiverse model that is met with the highest levels of skepticism.
Tegmark’s level 1 multiverse is a series of parallel universes that maintain the same (or at least very similar) physical constants as our universe but realize all initial conditions. That is to say, all possible realities, given our physical constants, are actualized in some other parallel universe. A universe in a multiverse such as this would look very similar to the one that we are currently in, save for different initial starting conditions. So, for example, while another universe would enjoy remarkably similar physical constants and laws of nature as ours, it would have a different initial starting point, making it, perhaps, at a point in development 2,000 years behind our universe, or perhaps 2,000 years ahead of our universe. The universes within this multiverse are inaccessible to other universes, and due to the rate of expansion and the distance between the universes, it would not be possible, says Tegmark, for one to ever travel between universes.
The level 2 multiverse is essentially composed of an “infinite set of distinct Level 1 Multiverses, each represented by a bubble . . . some perhaps with different dimensionality and different physical constants” (Tegmark, 2007, p. 105). Each bubble contains a distinct parallel universe that displays not only initial