By Kaitlin Smalley
Metaphysics has often concerned itself with an underlying unity to the world beyond the phenomena. What matters is how such a unifying metaphysics is sought and in particular whether it is hermetically sealed from science or integrated with it. – James Ladyman. 
Metaphysics is a notoriously difficult field to define. For the purposes of this paper, let us take for granted that metaphysics is, at the very least, a “part of our collective attempt to model the structure of objective reality.”  Typically, metaphysical questions ask about the existence and nature of things in reality, and of reality itself.  But so does science. So, what distinguishes metaphysical questions from scientific questions? Arguably, there exist some metaphysical questions that concern unobservable/intangible, immeasurable, and merely possible aspects of the objective world—aspects that seem unapproachable or worthless to scientists.  For example, is the objective world that science studies real? And in what sense? What does it mean for something to be real?
Since metaphysicists ask questions of things that are unobservable, they have traditionally resorted or been confined to reasoning purely a priori about the world.  However, since they are attempting to model the structure of objective reality, the conclusions they draw (ideally) claim something about the physical world. The question is whether or not this is problematic. If metaphysicists are using purely analytic reasoning to deduce synthetic truths, are their claims justified? This is the infamous epistemological problem of metaphysics, and is the reason philosophers began to question whether science might be sufficient to consume the field altogether (since science uses empirical research, it is often supposed its takeover would eliminate this epistemological problem). 
Believing the deduction of synthetic truths via analytic reasoning is problematic gives rise to the intuition that there must be some better way to answer metaphysical questions (assuming they are meaningful at all). If there were some better way, then it would need to allow metaphysicists to make justified claims about the objective world.  Science makes justified claims about the objective world (supposedly).  So naturally, one questions whether science could be the answer to this problem. Traditionally, philosophers have begun by asking whether we should use only scientific methods to investigate metaphysical questions, however, the first question we need to answer is whether science is capable of answering all metaphysical questions.
Responses to this line of questioning vary greatly. Some deny that there is even a problem by arguing that the metaphysical method of reasoning we label ‘analytic’ is in fact ‘synthetic’.  This is not widely accepted. Others deny that the epistemological problem of metaphysics suffices an appeal to science, because science itself is prone to a similar epistemological problem.  The argument provided for this is generally accepted, but viewed as not having much impact on the debate; for if this is the case, then still how do we go about answering metaphysical questions, and can science answer these questions?  Logical positivists and radical naturalists argue that the epistemological problem of metaphysics is a damning one, and as such, metaphysical questions may only be meaningfully answered by science, regardless of the cost.  Some of these philosophers go as far as to argue that the metaphysical questions that science cannot answer are meaningless.  Others again argue that the problem does call for an appeal to science; however, since (they also argue) there are metaphysical questions science cannot answer, the use of a priori reasoning is sometimes acceptable. 
None of these responses seem to argue that science can answer all metaphysical questions. In fact, they all seem to argue or suggest that, prima facie, science fails to do so. So, why are philosophers seemingly inclined to believe this?
Firstly, to borrow Carnap’s terminology, science does not appear to be able to answer ‘external’ ontological questions such as “are tables real?”  We don’t know how to agreeably define “real” from experience alone; we don’t understand what qualifies an object’s “reality” from observation alone; and we are therefore unable to justifiably measure whether an object is “real” or “unreal” using scientific methods alone. Some philosophers deny that this type of question has any weight to throw around the debate because it is linguistically meaningless.  If this is the case, there is still another problem that they must answer: how ought we to decide between rival scientific theories? Which theory’s metaphysical commitments ought the solely science-based metaphysicist to endorse, if science cannot determine which, if any, is true?  This is the problem of underdeterminism; science seems to underdetermine metaphysics.  The advocate of a solely science-based metaphysics must explain whether a metaphysicist can justifiably reflect analytically on unsettled scientific matters, and if not; why not?
A proposed solution to this problem has been to use science as a foundation for one’s metaphysics until a situation like this is reached. Once it becomes impossible to proceed using science alone, “traditional methods” (‘armchair’ reasoning) may justifiably be employed.  In this case, however, the claims arrived at via a priori reasoning are also demoted to the status of ‘analytic’. It is argued that we ought to acknowledge when a claim has been derived analytically, and that such a claim about the world is not justified; only speculative.  Traditional metaphysics here becomes a supplement to science and no more.  This final claim is obviously a contentious one, and it remains open whether it is and/or should be the case. 
In summary, it remains an open question whether traditional metaphysical methodology is acceptable, given what metaphysics is trying to claim. It also remains open to debate whether science should entirely replace the role of traditional ‘armchair’ reasoning in answering metaphysical questions. However, philosophers appear to agree that science underdetermines metaphysics in at least one way; namely, that science cannot answer all metaphysical questions.
Kaitlin is an Honours student in Philosophy, interested by most things, focused at the moment on the phenomena of epistemic injustice in educational settings. This paper has nothing to do with that, though. (Or does it?)
 James Ladyman, “Science, metaphysics and method”, Philosophical Studies (2012) 160:31-51.
 James Ladyman, D. Ross, D. Spurrett & J. Collier, “In Defence of Scientism”, Everything Must Go: Metaphysics Naturalized (2007).
 Peter van Inwagen & Meghan Sullivan, “Metaphysics”, The Stanford Encyclopedia of Philosophy (Spring 2015 Edition), Edward N. Zalta (ed.). Online at: <http://plato.stanford.edu/archives/spr2015/entries/metaphysics/>
 Hume believed the theories of traditional philosophers were “too speculative, relying on a priori assumptions…” (Morris & Brown, 2015) He also spoke specifically about the methodology of metaphysics: proposing “an empiricist alternative to traditional a priori metaphysics” in his Treatise in 1739-40 (Morris & Brown, 2015). Also: “Carnap… took the claims of physicists, unlike those of metaphysicians, to be in good epistemological standing.” (Ney, 2012, p54) See (Ney, p71) for further discussion of this topic.
 Whatever that means; I am sure a scientist, or neoclassical metaphysicist holds a very different idea of what qualifies as justification to an armchair metaphysicist.
 Ney explicitly states that “science can provide us with objective justification for its claims” (Ney, 2012, p62, footnote 9), and many people, particularly inside the science community, I am sure would agree. However, it is worth noting that this can be, and is actively being, questioned by philosophers of science.
 David Papineau, “The Poverty of Analysis”, The Aristotelian Society (2009) supp Vol LXXXIII.
 W.V.O. Quine, “Two dogmas of empiricism”, From a Logical Point of View (1951/1953).
 Alyssa Ney, “Neo-positivist metaphysics”, Philosophical Studies (2012) 160:53-78.
 Rudolf Carnap, “Empiricism, semantics and ontology”, Meaning and Necessity (1950/1988).
 Ney, “Neo-positivist metaphysics”.
 Carnap,“Empiricism, semantics and ontology”.
 One who commits themselves to using only science to answer metaphysical questions.
 Ladyman, 2012.
 This solution proposed by (Ney, 2012). However, notice that this solution in itself poses an epistemological problem of the kind: how do we know when we have reached the limitations of science? Otherwise, who decides when enough science is enough?
 “[We] should be more explicit and careful about when our positions lack empirical support and therefore are being proposed as something closer to a preference or attitude.” (Ney, “Neo-positivist metaphysics”, 77).
 “[It] is precisely the fact that physics is not yet complete that metaphysicians right now have something to contribute… this can help the physicist understand her own theories.” (Ney, “Neo-positivist metaphysics”, 77).
 I feel the need to note that such a view, as represented by Ney, relies upon empiricist conceptions of what constitutes knowledge. In fact, throughout this paper, most of the views I have referenced take for granted that the scientific method provides us with the most reliable methodology for constructing knowledge about the world. Something that remains to be questioned here, but deserves to be, is what counts as justification for that assumption, and whether there is an epistemological problem we might face when determining this.
Carnap, Rudolf, “Empiricism, semantics and ontology”, Meaning and Necessity (1950/1988)
Ladyman, James, “Science, metaphysics and method”, Philosophical Studies (2012) 160:31-51
Ladyman, J. Ross, D. Spurrett, D. & Collier, J. “In Defence of Scientism”, Everything Must Go: Metaphysics Naturalized (2007)
Morris, William Edward and Brown, Charlotte R., “David Hume”, The Stanford Encyclopedia of Philosophy (Fall 2015 Edition), Edward N. Zalta (ed.), URL = <http://plato.stanford.edu/archives/fall2015/entries/hume/>.
Ney, Alyssa, “Neo-positivist metaphysics”, Philosophical Studies (2012) 160:53-78
Papineau, David, “The Poverty of Analysis”, The Aristotelian Society (2009) supp Vol LXXXIII.
Quine, W.V.O, “Two dogmas of empiricism”, From a Logical Point of View (1951/1953).
Van Inwagen, Peter and Sullivan, Meghan, “Metaphysics”, The Stanford Encyclopedia of Philosophy (Spring 2015 Edition), Edward N. Zalta (ed.). Online at: <http://plato.stanford.edu/archives/spr2015/entries/metaphysics/>
Featured image by Kenyon Cox via Metropolitan Museum of Art