Characterizing naturalism
Many philosophers are committed to some kind of naturalism about reality. Characterizing naturalism, however, is not as easy as it might appear. Barry Stroud comments,
‘Naturalism’ seems to me in this and other respects rather like ‘World Peace.’ Almost everyone swears allegiance to it, and is willing to march under its banner. But disputes still break out about what it is appropriate or acceptable to do in the name of that slogan. And like world peace, once you start specifying concretely exactly what it includes and how to achieve it, it becomes increasingly difficult to reach and to sustain a consistent and exclusive ‘naturalism.’Footnote 1
Philosophical reference works seem to point in two different directions in their characterization of naturalism. Below are five examples that make this point, although we could bring in more.
(1) Philosophical naturalism is the view that an adequate philosophical account of the natural world, including humans, can be given solely in terms of objects and processes occurring in the natural causal order. No appeal to anything supernatural or transcendent is required.Footnote 2
(2) Naturalism, the two-fold view that (i) everything is composed of natural entities – those studied in the sciences (on some versions, the natural sciences) – whose properties determine all the properties of things, persons included, abstracta (abstract entities) like possibilia (possibilities) and mathematical objects, if they exist, being constructed of such abstracta as the sciences allow; and (ii) acceptable methods of justification and explanation are commensurable, in some sense, with those in science.Footnote 3
(3) Most generally, a sympathy with the view that ultimately nothing resists explanation by the methods characteristic of the natural sciences.Footnote 4
(4) Naturalism, in recent usage, is a species of philosophical monism according to which whatever exists or happens is natural in the sense of being susceptible to explanation through the methods which, although paradigmatically exemplified in the natural sciences, are continuous from domain to domain of objects and events. Hence, naturalism is polemically defined as repudiating the view that there exists or could exist any entities or events which lie, in principle, beyond the scope of scientific explanation.Footnote 5
(5) There are two main applications of the term ‘naturalism’ in modern philosophy, one in metaphysics, epistemology, and philosophy of mind and the other in ethics. What they have in common is the belief that the universe is all one, in the sense that all objects in it and all aspects of it are equally accessible to study by scientific method.Footnote 6
Naturalism, so characterized, involves both claims about the kinds of things that exist and commitments to a certain methodology. It is unclear from the definitions if one or the other of these two commitments is more fundamental. That is, is the commitment to the methods of science held largely or in part because those methods will not sanction supernatural or transcendent things, or is the commitment to the nonexistence of such things a result of the commitment to the methods of science? As we shall see, it is possible to take naturalism either as consisting more fundamentally in a claim about what exists, or as consisting more basically in a commitment to certain methods.
To think of naturalism as a claim (we shall call this ‘claim naturalism’) is to endorse something like the following: ‘Naturalism is most fundamentally the claim that the only kinds of things that exist are natural things. No supernatural or transcendent entities or processes exist.’ Taking it as a commitment to methodologies (‘method naturalism’) is to endorse something like the following: ‘Naturalism is most fundamentally a commitment to hold that whatever (and only whatever) the proper use of scientific methods leads us to believe about the world, in the long run, is what we ought to believe about the world.’ Method naturalism should not be confused with methodological naturalism, which is the position that one ought to adopt claim naturalism as a working assumption when doing science, whether or not one believes claim naturalism to be true. It is also the case that many claim naturalists take it that the mark of a natural entity or process is that it can be discovered or explained by the methods of science. Claim naturalism is distinguished from method naturalism, however, in that claims about what exists are more fundamental than the commitment to the scientific method.
The fine-tuning argument for God's existence
The advantages and the limitations both of claim naturalism and of method naturalism can be seen if we engage each with implications of the fine-tuning argument for God's existence. The fine-tuning argument for the existence of God has become perhaps the most popular version of theistic argument in contemporary philosophy of religion. It is a kind of design argument that does not fall to the challenges that neo-Darwinism raises to the traditional argument for design. The facts appealed to in the argument are not disputed. Daniel Dennett provides a clear characterization of the argument:
As more and more has been learned about the development of the universe since the Big Bang, about the conditions that permitted the formation of galaxies and stars and the heavy elements from which planets can be formed, physicists and cosmologists have been more and more struck by the exquisite sensitivity of the laws of nature. The speed of light is approximately 186,000 miles per second. What if it were only 185,000 miles per second, or 187,000 miles per second? Would that change much of anything? What if the force of gravity were 1 percent more or less than it is? The fundamental constants of physics- the speed of light, the constant of gravitational attraction, the weak and strong forces of subatomic interaction, Planck's constant – have values that of course permit the actual development of the universe as we know it to have happened. But it turns out that if in imagination we change any of these values by just the tiniest amount, we thereby posit a universe in which none of this could have happened, and indeed in which apparently nothing life-like could ever have emerged: no planets, no atmospheres, no solids at all, no elements except hydrogen and helium, or maybe not even that- just some boring plasma of hot, undifferentiated stuff, or an equally boring nothingness. So, isn't it a wonderful fact that the laws are just right for us to exist? Indeed, one might want to add, we almost didn't make it!Footnote 7
The argument claims that the improbabilities of the universe exhibiting this kind of precision by chance are too great to be reasonable. Therefore, it is more reasonable to think that the universe was finely tuned by an intelligent agent for the purpose of allowing life to develop. This argument provides a fulcrum for exploring the nature of naturalism. In what follows, the implications of the fine-tuning argument will be developed as it pertains both to claim naturalism and to method naturalism.
Claim naturalism
Understanding naturalism as a claim about what exists provides both advantages and disadvantages for the naturalist. One advantage of claim naturalism is that it straightforwardly captures our pre-theoretical intuitions about what naturalism ought to be. The opposite of naturalism is supernaturalism. A naturalist, then, does not think that any supernatural things exist. Naturalism, in this way, has been closely allied with materialism and physicalism. Most people have a pre-theoretical idea of which things are paradigm cases of the natural and which are paradigm cases of the supernatural. Items and processes on the natural list will include things like cats, evaporation, bicycles, and rocks. The list of supernatural things and processes will include Cartesian minds, angels, God, and divine intervention.
The claim naturalist cannot rely on her pre-theoretical intuitions, however. She needs to have a criterion to discern which entities or processes count as natural and which count as supernatural. Her criterion must be reasonable, and it must be fairly precise. As illustrated in several of the definitions cited, most claim naturalists appeal to the methods of science in this regard. This link between claim naturalism and science will result in some of the problems that face claim naturalism.
For example, if science provides the only or the most precise criterion for what counts as natural, then the natural/non-natural distinction can be only as sharp as the science/non-science distinction. If the distinction between what is genuine science and what is not is vague, the line between what is natural and what is not will be similarly vague. If science cannot be precisely demarcated, neither can naturalism. The fact that there are vague boundaries between what is clearly science and what is not is not a problem for science itself. Nor is it a problem for method naturalism. It does become a challenge if there is an ontological claim tied to the results of science. Claim naturalism is an ontological claim. The only things that exist are those things that can be discovered or understood by application of scientific methodologies. Since there are no sharp boundaries between which methodologies count as science and which do not, the answer to the question of what exists will also not be precise. Although most cases will be clear, some will not be. In the vague cases we may be unsure whether to countenance such entities in our ontology. We cannot settle the matter until we have some kind of clarity, not only about the strength of the evidence for the entity, but also about the classification of the evidence. If it ever happens that what looked like very strong scientific evidence is revealed to be not scientific at all, then the entity supported by the evidence must be thought not to exist, even if the evidence for its existence remains strong.
Fine tuning and claim naturalism
The fine-tuning argument reveals another, particular disadvantage of claim naturalism. Obviously, if the argument makes it reasonable to think that a designer of the universe exists, then it supports the conclusion that claim naturalism is false. God, if He exists, is the clearest possible example of a supernatural entity. What is important here, however, is that the best or most popular response taken by the naturalist also may involve the existence of non-natural things. This response is the many-worlds hypothesis. If the many-worlds hypothesis is true or well-supported, the inference to purpose and therefore a designer is undermined considerably. The cost of thinking that the many-worlds hypothesis is true is that one must hold that there actually exists (or did exist) a vast quantity of worlds or universes. These worlds are odd entities for naturalists to believe in. To be sure, the many universes do not show up on anyone's pre-theoretical list of supernatural (or non-natural) items. As a result, they do not seem at first glance to be non-natural. A good case can be made, however, that they are non-natural indeed.
First, none of the other worlds are causally accessible to us. Most of them will have collapsed nearly immediately or expanded too quickly to allow star formation. The few that are stable are outside our space-time universe and causally disconnected from our universe. Therefore, they are outside of our empirical epistemic range. They are outside our epistemic range, not because we have not figured out how to find them, but because they cannot be found. It is physically impossible that we could get any empirical information from any cosmos but our own. As David Armstrong indicates, ‘these entities lack causal power in the space-time world’.Footnote 8
Second, the laws of physics in these worlds, if there are any laws at all, are different from the laws in our own universe. If the methods of science involve explanation by appeal to physical laws that are in continuity with those we have discovered, then the many universes fall outside those methods. Note the description of the methods of science in our definitions above. For example, an adequate account of everything ‘can be given solely in terms of objects and processes occurring in the natural causal order’ (1); and items studied in the sciences are those ‘whose properties determine all the properties of things’ (2). They are ‘susceptible to explanation through the methods which, although paradigmatically exemplified in the natural sciences, are continuous from domain to domain of objects and events’ (4). Finally, ‘all objects in it and all aspects of it are equally accessible to study by scientific method’ (5).
These definitions are not authoritative in any sense, but they do indicate the prevailing notion that the methods of science, insofar as they appeal to laws, appeal to the same laws we observe in our universe. There is a strong emphasis on continuity throughout the domain of the methods of science. It is a matter of conceptual necessity, however, that nearly every one of the various universes has different laws of nature, if they have any at all. As a result, the kinds and properties of objects that exist will differ widely from cosmos to cosmos. These differences indicate that it is quite a stretch to think that the many-worlds hypothesis postulates only entities of the sort approved by the methods of science.
Although a full challenge to the claim that the many worlds meet the requirements for being natural entities is beyond the scope of this essay, we have seen that there are reasonable grounds to think the many-worlds hypothesis does not constitute a naturalistic alternative. In light of these kinds of concerns, William Lane Craig has claimed that ‘the Many-Worlds Hypothesis is no more scientific, and no less metaphysical, than the hypothesis of a Cosmic Designer’.Footnote 9
The fine-tuning argument, then, provides a significant challenge to claim naturalism. The evidence for fine tuning supports the claim that either a designer/creator exists or that a vast array of other universes exists. In either case, the evidence supports the existence of things that are not naturalistic. Therefore, naturalism, as a claim about what exists, faces significant counter-evidence.
Method naturalism: van Fraassen and Rea
In recent years, two major works have characterized naturalism in terms of methods rather than in terms of claims. Bas van Fraassen has argued that naturalism is a stance.Footnote 10 Michael Rea has defended the idea that naturalism is a research programme.Footnote 11 Van Fraassen is a proponent of naturalism, so understood. Rea thinks that taking naturalism as a research programme puts it into the strongest possible position. Despite this fact, he is critical of naturalism.
Van Fraassen has argued that naturalism and other related views such as empiricism and materialism are not positions after all.Footnote 12 Rather, they are commitments or stances. Although he casts his discussion in terms of materialism, he takes it that naturalism boils down to materialism in the end.Footnote 13 Van Fraassen introduces the idea of a stance as follows:
Does the thesis that matter is all there is rule out at least some kinds of theories, so that they are not even candidates for scientific exploration? I will argue that this is quite illusory. There may, however, be a certain orientation, attitude, or stance associated with this thesis – which does affect science as well as practical and intellectual life generally – for which this thesis functions as a code.Footnote 14
He explains this stance as follows:
Hence, I propose the following diagnosis of materialism: it is not identifiable with a theory about what there is, but only with an attitude or a cluster of attitudes. These attitudes include strong deference to science in matters of opinion about what there is, and the inclination to accept (approximative) completeness claims for science as actually constituted at any given time.Footnote 15
The thesis that ‘matter is all there is’, then, is not a factual claim. It expresses, rather, a stance towards the world. It is a commitment to think about the world from a particular viewpoint. This viewpoint is not a claim about the way things are. It is a systemic deference to the current sciences to adjudicate disputes about the way things are. As a stance, naturalism can be neither supported nor countered by empirical evidence. Phrases such as ‘matter is all there is’, and ‘the only things that exist are natural things’, turn out not to be claims but to be names. They are names of the materialistic and the naturalistic stances respectively. As names, they cannot be true or false. They simply pick out the respective stances.
Any stance of this kind is broad enough or has boundaries that are elastic enough to absorb just about any empirical or theoretical counter-evidence. Naturalism, then, is tremendously malleable and will ‘retrench’ in order to appropriate whatever difficulties are encountered. Precisely what one who takes the naturalistic stance will accept or will reject will develop over time. Just as modern science has retrenched to allow for electro-magnetism, quantum events, and relativity, so naturalism will retrench to allow whatever recalcitrant entities we need to allow.
Van Fraassen recognizes that his view has the effect of ruling out any arguments that attempt to show that naturalism is false:
If this is correct, no such argument as Plantinga has recently given against naturalism can succeed. For this argument hinges on reflections on the probability of certain events on a supposition which includes philosophical naturalism. That makes sense only if naturalism is an identifiable thesis, a factual assertion. Even if the argument is internally correct, therefore, it is no more effective against naturalism than points about quantum theory are against materialism – they affect only some temporary tradeable asset of the position.Footnote 16
Specifically, he is responding to Plantinga's ‘evolutionary argument against naturalism’.Footnote 17 No argument against naturalism can refute naturalism because naturalism is not a position to be refuted. Although van Fraassen does not acknowledge the fact, on his view such arguments are not without value. Their value will be that they establish the direction in which the retrenchment of naturalism must proceed. My consideration of the many-world hypothesis shows that naturalism must develop in the direction of accounting for the existence and nature of physical universes that both are causally disconnected from our own and have laws that are significantly different from the laws in our universe.
Michael Rea has defended the notion that naturalism is a research programme. In short, a research programme is a ‘set of methodological dispositions’.Footnote 18 These dispositions involve commitments to take certain sources of evidence as basic and to take others as not basic. For a source of evidence to be basic is for its reliability not to require justification from more basic sources. For example, if one took sense perception as basic, one would believe what sense perception delivered without requiring that sense perception be validated. This same person might take historical investigation as a non-basic source of evidence. A particular historical investigation will be considered reliable only if it is grounded on the evidence of the senses (or on the evidence of other, more basic sources).
Rea is careful to distinguish his use of the term ‘research programme’ from that of Imre Lakatos. Lakatos includes claims that are believed as well as basic methodologies as part of his understanding of a research programme. Rea does not. One subscribes to a research programme before one begins any investigation. Therefore, one does not choose a research programme on the basis of evidence. One must already have a research programme to take any item to count as evidence. Rea claims that ‘evidence can only be recognized as such from within a research program’.Footnote 19
Rea does allow that it is possible to discard a research programme on the basis of evidence. A person might find one basic source of evidence coming into conflict with another. The person will revise her research programme accordingly. Perhaps, rather than taking every belief formed on the basis of sense experience to be true, she will take those to be true only when the perception is clear. In this way, her research programme has been revised. Rea emphasizes that while the original research programme is rejected on the basis of evidence, the revised research programme is not adopted on the basis of that same evidence. The evidence only counts as evidence in the context of the original research programme. It does not count as evidence for the new programme. Rea does not claim that simply anything goes in adopting a new research programme. The grounds for adopting a new research programme are not evidential; they are pragmatic.
The claim that naturalism is a research programme means that it is a set of dispositions regarding sources of evidence. In short, Rea claims that naturalism is the disposition to take as evidence what science tells us: ‘Thus, I argue, the fairest and most plausible characterization of naturalism treats it as a research program – in particular, a research program wherein one treats the methods of science and those methods alone as basic sources of evidence.’Footnote 20 Although many research programmes might take the methods of science as basic sources of evidence, what is characteristic of naturalism is that these methods are the only basic sources. This aspect of Rea's characterization is reflected in some of the definitions cited, as well. Adopting this kind of method naturalism, then, will not be a matter of assessing evidence. At best, there are pragmatic considerations in terms of the consequences of the programme.Footnote 21
The defining feature of method naturalism for both van Fraassen and Rea, as we have seen, is a commitment to follow the methods of science wherever they lead. As far as thinking about reality and what it is like is concerned, there are no methods other than those sanctioned by science that will be employed. Method naturalism, then, is an epistemological rather than a metaphysical posture.
One advantage of method naturalism, whether of van Fraassen's variety or of Rea's, is that it is impossible for naturalism, so understood, to come apart from the scientific methodologies. Rea introduces this feature as a challenge to what I am calling claim naturalism:
So those who want to formulate naturalism as a thesis face a dilemma. On the one hand, if they formulate it as a thesis that cannot be overturned by scientific investigation, then naturalism turns out to be precisely the sort of thesis that naturalists are unwilling to accept. In the worst cases such formulations are either vacuous or self-defeating. On the other hand, if they formulate it as a thesis that could be overturned by scientific investigation, then (obviously enough) naturalism stands at the mercy of science.Footnote 22
Claim naturalism is a position that can, conceivably, come apart from the sciences. Even though most claim naturalists use the methods of science to determine which events and objects count as naturalistic and which do not, it is possible for this connection to unravel. If there was scientific evidence for some non-naturalistic entity, for example, science itself would contribute to undermining claim naturalism. I argued above that the fine-tuning argument provides this kind of scientific evidence. It strongly establishes that either a supernatural agent exists or exceedingly many universes exist that are causally and nomologically disconnected from our own. In either case, scientific evidence points away from straightforwardly naturalistic entities.
Another advantage of method naturalism is that it captures how a position such as naturalism or, for that matter, theism functions. These kinds of positions do function, at least in part, as stances or programmes. Such positions are broader than a single claim. They are often called, ‘world-views’. A world-view is a total way of looking at the world. Central to any world-view are commitments that play a governing role. For a materialist, the thesis that matter is all there is will play such a role. How the materialist thinks about bio-ethics or aesthetics or values or the practice of science will be informed by this commitment. For the theist, the existence and nature of God plays a similar role. Van Fraassen recognizes this similarity: ‘Being or becoming an empiricist will then be similar or analogous to conversion to a cause, a religion, an ideology, to capitalism or to socialism, to a worldview such as Dawkins's selfish gene or the view Russell expressed in “Why I Am Not a Christian”.’Footnote 23
One disadvantage of method naturalism is its characterization as a stance (or a research project) and nothing more.Footnote 24 The fact that naturalism does function as a stance does not imply that it is nothing more than a stance. A stance may also involve factual claims. As Plantinga points out in his response to van Fraassen's essay:
Materialism thus thought of has or may have ‘cognitive content’; it needn't be so vague as not to eliminate anything. Perhaps there are no explicitly stateable and reasonably precise necessary and sufficient conditions for something's being material but there may be necessary conditions. If materialism is true, for example, there won't be any such person as the God of traditional theism; no all-knowing, everlasting, all-powerful, and wholly good being who has created the world.Footnote 25
One can hold that the way naturalism works out in practice indicates that it is not merely a factual claim without concluding that it is a stance and nothing more. Perhaps it can be both a stance and a claim or a stance with factual implications.
Fine tuning and method naturalism
The fine-tuning argument provides its own challenge to method naturalism. This challenge is best seen when we introduce an objection to my previous claim that the many universes are not naturalistic entities. Perhaps we ought to think that the various universes are within the reach of science, despite their causal and nomological disconnect from our own world. The existence of these worlds, it can be claimed, is implied by our best physical theories. The empirical findings that are employed in the fine-tuning argument support the claim that the vast array of universes exist.Footnote 26 This implication might be thought to be sufficient to show that the many universes count as natural things.
In response, I would stress that the existence of the many universes is not implied by the empirical findings. What is implied by the evidence is the truth of a disjunction: either the many universes exist or a designer/creator of our universe exists. The findings themselves, that is, our best physical theories, give us no grounds to prefer one of these hypotheses to the other. If we prefer to believe in the many universes rather than in a designer of the universe, it will be due to other considerations such as our pre-theoretical sense that a designer is a supernatural being. If being implied by our best physical theories is what justifies calling the many-universe hypothesis a naturalistic hypothesis, then the cosmic designer/creator counts as a natural entity as well. The preference for the many-universe hypothesis over the design hypothesis is not supported by the fine-tuning argument itself.
This objection to my challenge to claim naturalism, then, is not sound. What it shows is that method naturalism forces us to grant that both the many universes and God fit into the naturalistic world. There is something that should be upsetting for naturalism if God can count as a naturalistic entity. Our characterization of naturalism in this case has little connection with our pre-theoretical understanding. Yet the method naturalist does not have the resources to resist this result. Quine has indicated, however, that such a result would not concern him: ‘If I saw indirect explanatory benefit in positing sensibilia, possibilia, spirits, a Creator, I would joyfully accord them scientific status too, on a par with such avowedly scientific posits as quarks and black holes.’Footnote 27
In fact, there are considerations that ought to lead the method naturalist to prefer the God hypothesis to the many-world hypothesis. In the course of our discussion, we have uncovered three marks that indicate that an item or process can be investigated by the methods of science. These are the causal connection with objects and events in our universe, the application of the same laws of physics, and being implied by our best physical theories. As far as the last mark is concerned, as we have seen, there are no grounds for preferring one of the theories or the other.
As far as causal connection is concerned, a designer is more closely connected causally with the world than the many universes. The role of the designer as supported by the fine-tuning argument is to bring the universe into existence with the very specific properties that it has. This task is a straightforwardly causal one. There is a close causal connection, then, between the designer and our universe, if the designer hypothesis is true. If the many-world hypothesis is true, there is no causal connection between our world and the other universes.
The application of physical laws to the designer is problematic to be sure. It is not clear that it is problematic in the sort of way that would make one prefer the many-world hypothesis, however. There are two reasons that physical laws do not apply to the designer. The first is that the designer is the creator of the laws and, thus, stands outside them. This consideration does not lead one to prefer the many-world hypothesis. Rather, it reveals that the designer hypothesis and the many-universe theory are on a par. Neither a designer nor the many universes are susceptible to analysis by appeal to laws.
The second reason that physical laws do not apply to the designer is that the designer is a personal agent. It is not clear that personal agency falls under physical laws in the way non-personal events do. We have ample empirical knowledge of personal agents, and this knowledge indicates that agency is resistant to analysis strictly according to physical laws. Although many thinkers will revise their understanding of persons to eliminate those aspects of agency that resist explanation by laws, others will accept the idea that personal agency in general stands outside those things that are explained by appeal to law.Footnote 28 If the designer exists, this aspect of its agency is not significantly unlike the sort of agency we encounter. As far as its personal agency is concerned, then, the designer hypothesis fits more neatly than the many-world hypothesis into the world as we know it.
Conclusion
Method naturalism, it seems, has hit a wall. Any form of naturalism that allows a God who creates to count as a natural entity barely warrants the name naturalism. Perhaps method naturalism turns out to be a moderate sort of scientism. Moderate scientism could be seen as a stance or a research project that consists of the commitment to follow scientific evidence wherever it leads while remaining open to the possibility of entities which seem, at least pre-theoretically, to be supernatural.
The philosopher who wishes to maintain naturalism, then, might best hold tentatively to claim naturalism. She will have to live in the hope that a criterion that is both reasonable and precise will be found to distinguish natural things from non-natural things. This criterion will have to be reasonable enough not to appear ad hoc. It will have to be precise enough to determine that the many universes are natural but the designer is not. So far, the methods of the sciences are not sufficient.Footnote 29
