Empiricism: Reloaded

Transcription

1 Book Review Empiricism: Reloaded Paul Studtmann (2010) Empiricism and the Problem of Metaphysics, Lanham, MD: Lexington Books, 180 pages, index. Studtmann s Empiricism and the Problem of Metaphysics (hereafter EPM) is a lively reformulation of the empiricist challenge to metaphysics. Hume s famous version rejected anything that was not either experimental reasoning concerning matter of fact and existence or abstract reasoning concerning quantity or number (Inquiry Concerning Human Understanding, Section XII, Part 3). That was 1748, and the intervening period has seen a variety of re-statements of the challenge, especially by some of the logical empiricists and by Quine, as well as defences of metaphysics, perhaps most notably in recent decades by David Lewis. Just as importantly, a great deal has happened in science, logic and mathematics since Hume. This means that reasoning concerning matters of fact and abstract reasoning concerning quantity or number aren t what they used to be. Finally, open and un-embarrassed metaphysical debate is striking feature of Anglophone philosophy over the past few decades. For these reasons Studtmann s book is rather timely. Studtmann glosses the general problem of metaphysics as determining whether, and why, metaphysics can yield a set of well-confirmed theoretical results (EPM, p. 4). A thorough response to the problem of metaphysics at least for an antimetaphysical empiricist has to deal with each of three more specific problems relating to metaphysics: delineation, critique, and stance. Roughly they are the problems of saying what metaphysics is, specifying what is wrong with it (and why), and determining what the proper attitude to metaphysical theorising is. The most interesting parts of EPM are to be found in the connected treatment of the problems of delineation and critique. Metaphysical debates, proposes Studtmann, implicate modal concepts (EPM, p. 13f) which means, among other things, seeking knowledge of the modal status of some sentences (for example whether there is a necessarily existing being is itself necessarily true). Unlike Hume s characterisation, which specifies which books not to burn, this one is positive. Studtmann defends his delineation over chapters 4, 5 and 6 of EPM, arguing that a number of 1

2 paradigmatic metaphysical debates, as well as some in epistemology and ethics, implicate modal concepts in the required way. The function of modal concepts in these debates, proposes Studtmann, is in validating information-increasing inferences (EPM, p. 14). The formulation in terms of information is motivated partly in order to remain agnostic about psychological specifics. (Whether or not ideas and impressions make a come-back, psychological science will continue to recognise some information-carrying cognitive states.) The information talk is also supposed to do some heavy lifting. Here is a very broad sketch of the position. Information we get via the senses is (obviously) legitimate for empiricists. Some inferences especially first order extensionally valid ones are what Studtmann calls information decreasing (because one sentence validly entails another iff the set of models in which the latter is true is a sub-set of the models in which the former is true). These inferences require no special epistemic treatment, given that there are finite procedures for checking validity, and presumably Studtmann does not explicitly specify this as long as the information going in has a suitable sensory pedigree. With numbers treated adjectivally, sentences in finite arithmetic are also either valid or invalid (so, contra Kant, 7+5=12 is finitely valid, and requires no synthetic a priori). The same does not hold, of course, for arithmetic including axioms that quantify over infinite totalities, where finite procedures cannot decide validity, of which more anon. We can and sometimes do refer to deductively valid first-order arguments, and to theorems of finite arithmetic as necessary, but the necessity talk here is optional. This is not so for all cases where we are inclined to speak of necessities. Some sentences seem intuitively necessary ( Nothing is red all over and blue all over ) just as others seem intuitively contingent ( Peter is 5 feet tall ). Studtmann maintains that there are inferences that seem intuitively valid, but are not information decreasing, and offers inferring Socrates is unmarried from Socrates is a bachelor as an example. Here, he wants to say, the concept of necessity seems to have a clear and ineliminable role, because an un-stated premise to the effect that (x)(if x is a bachelor, then x is unmarried) validates the inference (EPM p. 31). This way of putting things is at least slightly quirky. Single sentences don t standardly entail more than they say, and paradigmatically valid inferences have two or more premises. (So Socrates is taller than Meletus is validly inferred from both Socrates is taller than Plato and 2

3 Plato is taller than Meletus, but not from either alone.) In Studtmann s specific example, the inference also turns out valid with the additional non-modal that (x)(if x is a Bachelor, then x is Unmarried). Studtmann s point, though, is that modal premises themselves are information increasing relative to what can be justified by experience, including finite logical operations on information from experience. (A putatively necessary sentence inferred from no other premises also gets called valid EPM, p31.) Studtmann s approach to the critique problem is two pronged. His shallow solution is to claim that modal concepts (that cannot be cashed out as first order validities or deflated in other ways) are theoretically illegitimate where this is understood as being an empirical claim that they won t find a stable home in the progressive development of scientific (and mathematical) theory. This is an empirical bet, which he does not directly defend. He also offers a deep solution, which is an argument concluding that all a priori knowledge is knowledge of the results of effective procedures (EPM, p. 18). This formulation seems paradoxical, but it means that scientific and mathematical knowledge taken as a priori will turn out, if it is indeed knowledge, to be the result of finite validity-establishing procedures, and so information decreasing. If true, this would explain the shallow solution. Rationalists disagree, holding that some means or other (such as rational intuition) warrants beliefs that go beyond what effective procedures can establish. By putting things in terms of information, it elegantly turns out that rationalists suppose themselves to have the abilities of what Turing called Oracles imaginary machines stipulated by fiat to be able to solve a decision problem after a single processing step, including a non-computable problem such as saying of some other machine whether it would halt on a given input or not. That is to say, although Studtmann does not put it exactly this way, Oracles are allowed to be hypercomputers, and rationalists (and anyone else holding modal beliefs to be justifiable) effectively take themselves to have some hypercomputational (Church-Turing thesis violating) powers. The argument for this proceduralist account of the a priori (which excludes Oracular knowledge, and effective procedures for modal claims) depends on the assumption that scientifically used information has sensory origin. This does not so much beg the question as make clear the challenge to the non-empiricist: Epistemically to justify a source of information that is both non-sensory and specifically capable of supporting modal knowledge. 3

4 This, Studtmann says, is the form of a solution to the problem of metaphysics, because he does not engage in substantial defence of the empirical premises. Empiricist philosophy of science provides, unsurprisingly, some support here. Van Fraassen (1987) maintained that accepting a scientific theory requires no more than recognising it as (if it is indeed so) empirically adequate to observable phenomena, and stops short both of realism about parts of theories concerning unobservables, and claims to modal knowledge. To be an empiricist is to withhold belief in anything that goes beyond the actual, observable phenomena, and to recognise no objective modality in nature (1987, p202-3). As Studtmann does, although with more detail, van Fraassen recognises that there is modal talk in science, but both urge against treating it as knowledge: modality appears in science only in that the language naturally used once a theory has been accepted, is modal language (The Scientific Image, p198). If Studtmann is correct (enough) about delimiting metaphysics, and the illegitimacy of modal concepts then the position of one aspiring to metaphysical knowledge is somewhat analogous to that of the Platonist according to Benacerraf (1973, see EPM, p58). Objective modal facts, like Platonic forms, have inadequate evidential footprints. It is worth noting that the epistemic challenge remains even for in some respects rather liberal versions of empiricism. Suppose, for example, an empiricist who was willing to count any set of contraptions that transduced physical information into human neural information as a sense organ. She would regard the mammalian eye, and the eye plus a telescope, and maybe even the eye plus the Large Hadron Collider (and the computational paraphernalia needed to present data from it) as all equally acceptable sense organs. Consequently she d regard some things (electrons, genes) as observable that are not observable for Van Fraassen, and others (the moons of Jupiter) as already observed. But she d be no better placed when it came to modal knowledge, or knowledge of mathematical assertions about completed infinities. In making this sketch I ve left out a great deal. Empiricism and the Problem of Metaphysics moves along at a cracking pace, is occasionally genuinely funny, and touches briefly on a very wide range of topics, including sub-arguments relevant to modal logic, additional challenges to claims of modal knowledge, and wider philosophical, mathematical and logical debates. Gödel turns up as a surprising ally of empiricism (EPM, p60-63). Inevitably many points are covered very briefly, and some conclusions are defended rather cryptically. The most obvious ways to refute the overall conclusion (at least without rejecting its terms) are either to produce a counter-example to the shallow solution, which is to say a modal concept 4

5 that is genuinely theoretically legitimate in science (or mathematics), or a credible modal epistemology. The latter task hardly looks promising for any position worth calling empiricist. Studtmann s proposed response to the stance problem is what he calls moderate silentism. This recognises metaphysical claims as meaningful, and metaphysical speculation as conceptually illuminating and even fun. It acknowledges the robust appearance of necessity as a psychological fact about us, but since modal concepts aren t legitimate is not concerned to assign any sort of truth-value to modal discourse (EPM, p21). This is milder than calling for metaphysical texts to be committed to the flames, and than denying that metaphysical claims are cognitively significant. It is self-consciously close to the attitude Hilbert (1926) recommended for the infinite. In that, it is a robust denial of modal realism, just as an empiricist position should be. David Spurrett (Philosophy, University of KwaZulu-Natal) spurrett@ukzn.ac.za References Benacerraf, P. (1973) Mathematical Truth,The Journal of Philosophy, 70(19), pp Hilbert, D. (1926) Über das Unendliche, translated as On the Infinite in van Heijenoort, Jean (ed.), 1967, From Frege to Gödel. A Source Book in Mathematical Logic, , Cambridge, Mass.: Harvard University Press van Fraassen, B. (1987) The Scientific Image, Oxford: Clarendon. 5