On metaphysical equivalence, primitiveness, and theory choice.
Springer, 2016

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Review by Tuomas Tahko (Notre Dame Philosophical Reviews)

Metaphysical theories are beautiful. I mean it literally. At the end of this book, I defend the view that metaphysical theories possess aesthetic properties and that these play a crucial role when it comes to theory evaluation and theory choice.
But this is the end of a long journey – a journey that is perhaps more important than the destination. Before we get there, the philosophical path I propose to follow starts with three discussions of metaphysical equivalence. I argue that there are cases of metaphysical equivalence, cases of partial metaphysical equivalence, as well as interesting cases of theories that are not equivalent. Thus, claims of metaphysical equivalence can only be raised locally. My slogan is : the best way to do meta-metaphysics is to do first-level metaphysics.
To do this work, I focus on the nature of primitives and on the role they play in each of the theories involved. I emphasize the utmost importance of primitives in the construction of metaphysical theories and in the subsequent evaluation of them.
I then raise the simple but complicated question: how to make a choice between competing metaphysical theories? If two theories are equivalent, then perhaps we do not need to make a choice. But what about all the other cases of non-equivalent "equally good" theories? I use some of the theories discussed in the first part of the book as examples and I examine some traditional meta-theoretical criteria for theory choice (various kinds of simplicity, compatibility with physics, compatibility with intuitions, explanatory power, internal consistency,...) only to show that they do not allow us to make a choice.
But if the standard meta-theoretical criteria cannot help us in deciding between competing non-equivalent metaphysical theories, how then shall we make that choice? This is where I argue that metaphysical theories possess aesthetic properties – grounded in non-aesthetic properties – and that these play a crucial role in theory choice and evaluation. This view, as well as all the meta-metaphysical considerations discussed throughout the book, then naturally lead me to a form of anti-realism, and at the end of the journey I offer reasons to think better of the kind of anti-realist view I propose to embrace.