This new book of Tuomas Tahko opens a relatively untouched arena of the philosophical range of disciplines, one that has come to be called “metametaphysics” or otherwise known as “meta-ontology”. This introduction is more than needed! Even philosophers tiptoe in these matters, as the debate holds a very high level of complexity and it is easy to feel confused and downfall in the apparent oddity of the type of examples and theories that there are. This is why Tuomas Tahko helps the reader by having a very didactic introduction that guides us in the deep waters of the metaphysics that has resulted of years of lively debate within the analytic tradition. The term ‘metametaphysics’, however, cries for clarification: can we legitimate, at all, talking of metaphysics after the criticisms against the discipline itself offered by early critics? Or should we not reformulate these problems by throwing away the old terminology? Here as elsewhere, getting rid of the baby with the bathtub is a constant temptation: we should care about metaphysics (and metametaphysics) because we are interested in answering what there is. We are too required to carry this task in a systematic and ordered way, and we think we can actually approach that question by establishing categories and conceptual norms that tell us what has the right to be called an ‘object’, an ‘entity’, an ‘item’, etc. Tuomas Tahko defines the discipline as:

Metametaphysics= _df The study of the foundations and methodology of metaphysics. (Tahko 2015, 5)

By the definition one can observe that a metametaphysical attitude is a way of considering the whole metaphysical enterprise, to explore its methods and foundations. The term is, however, somewhat vague, as a good deal of first order metaphysics is contained in such task. Tuomas explains us why he does not want to use the other common term of ‘metaontology,’ so previously popularized by Quine. ‘Metaontology’ seems confined to the question of what there is -as metametaphysics does; but metametaphysics is a broader inquiry, as it also concerns the kinds and categories of what there is.

In Chapter Two, devoted to the discussion between Quine and Carnap -that saw the discipline emerge- and also concerned about taking Alexious Meinong’s position seriously, and language pluralism, Tahko shows us that the debate could be deceiving: according to Carnap, for example, questions such as “Do numbers exist?” should be addressed by talking about language. The discussion, however, shows that this is not satisfactory, and thus the discipline of meta-metaphysics starts to unpack in the discussion of what the structure of reality is, and how, thus, we can start to answer questions like the above (about the existence of numbers). Chapter Three shows that one has to start by defining our ontological commitments, and the use of quantifiers raises the problem of ‘quantifier variance’ and other issues that deal with questions about existence and their legitimacy. Ways of answering this are explained further in Chapter Four, in which the metametaphysical positions of Ontological realism, deflationism and conventionalism are introduced. These positions are assessed one by one showing that a very broad conception of Ontological realism is desirable if we want to carry forward and not ignore the challenges that reality posses to science and other human endeavors. Chapter Five shows that if we proceed deeming metaphysics seriously, the problems of clarifying grounding and logical dependence, truthmaking, causation, reduction and essence become prominent. Tahko cares to help us with a fresh prose and the introduction of definitions to see how these problems come together in the discipline.

Chapter Six: “Fundamentality and levels of reality”, concerns of the possibility of a hierarchy or a structure of levels that might be present in reality.

Tuomas helps us to understand how infinite regress lurks around the corner when we forget to care about a bottom line of what counts as a category, or a purely logical element that we ought to consider, in a given context, as ultimate (provided a universe at large in the top tier or the fundamental particles in the bottom tier). The options are presented, but the reader will be offered of abundant literature that renders witnessing where the debate is leading.

Is metaphysics a priori or a posteriori? This is another fascinating question that needs special guidance. Tahko helps us, in Chapter Seven, to understand that different approaches show that the presumably a priori or a posteriori character of metaphysics needs to be approached first and foremost by clarifying our use of these categories. Once this use is meta-metaphysically clarified we will be in good conditions to choose if we incline the scale in either side, and thus assume consequences of a hypothetical inclination. Thus, we can notice, on the one hand, that the metaphysics that inclines to the a priori might turn out to give a particular relevance to modality and therefore tell us what is possible or necessary in metaphysics. On the other hand, we could discover -following a posteriori inclinations- that metaphysics ought to follow science very closely, that way it can be revised according to what scientific inquiry demands in terms of defining categories and its objects of study, or maybe by requiring the help of metaphysics to clarify what view of the world follows from adopting such and such scientific view.

The role of intuitions and thought experiments in metaphysics is another hugely contested problem: Tahko shows us, in Chapter Eight, that metametaphysics will have to become epistemology in order to see what counts as a genuine source of metaphysical knowledge. Even a philosophical discipline as new as Experimental Philosophy is brought to the argumentation.

Finally, Chapter Nine deals with the deep problem of demarcation: Can metaphysics be naturalized? If so, how much? Tuomas proposes a moderately naturalized metaphysics stance to offer us a conclusion that connects the healthy relationship of science and metaphysics not as a servile dependence in either way, but as a mutually informing relationship that takes care of a particular set of questions. The range of the metaphysical questions would be, thus far, easily identified after touching the different specific metaphysical topics contained in this introduction.

One of the many assets of the book is Tahko’s habit of introducing definitions to the relevant terminology, these same definitions are gathered in a very handy glossary that collects them for a continuous double-check and consult, in case we want to trace our steps: many of these definitions are, obviously, just to introduce a discussion in a topic that may spiral into many more conflicting positions. Along with this habit of helping with a handy and working definition there are more theoretical virtues of the book that I want to point out: simplicity, explanatory power, internal consistency, empirical adequacy and so on… Indeed, Tahko aims to make an accessible introduction, but the articulation of both the chapters and discussions contained is such that one can travel back and forth across to earn a better picture of a problem: such is the case for the problem of ontological realism, which we come across in the book in many ways.

Some more philosophically trained readers could complain that there is little engagement with the ancient tradition of Aristotelian or Medieval metaphysics, or that Tahko only introduces problems in which he does not take a position, but this would be unfair, as the book tries to show us what is going on in a very contemporary debate. In addition, in commenting our book it would be more harm than help to take a definite position in many of these matters: an introduction requires the best kind of impartial judgment we need, and also a panoramic view that can be digested by anybody that wishes to get the gist in such complex discussion.