Naturalism

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NATURALISM

Put most succinctly, metaphysical naturalism affirms that the natural world is the only real one, and that the human race is not separate from it, but belongs to it as a part. The term naturalism refers also to an aesthetic style in literature, drama, and painting, and in ethics, to the theory that the full meaning of value concepts such as good and evil can be spelled out using only terms from a natural, or factual vocabulary. These are not of concern here. What follows is a discussion of naturalism in metaphysics and epistemology.

Everyone has a rough working notion of what can happen in the course of nature, and is familiar with the idea that perhaps a transcendent or supernatural realm lies beyond nature, another world that may occasionally make contact with the everyday world by, for example, miraculous interventions. Yet the distinction between what is natural and what is not needs to be made with some care. As St. Thomas Aquinas pointed out, everything that happens is in some way natural. Thus, according to classical philosophical theology, God must always, of necessity, act in accordance with his own nature. So from the divine point of view, special miraculous intervention, or general providential guidance, lies entirely within the realm of what happens according to nature.

What is needed is the conception of a world all of whose normal workings count as natural, while whatever lies outside this limit does not. The space-time world, with its material constituents working according to the laws of cause and effect, seems a good place to start. The natural world is the world of space, time, matter, energy, and causality, and naturalism affirms that this natural world is the only one there is. Yet even here care is needed: In some modern interpretations of quantum theory, the so-called Many Worlds interpretations, this particular space-time world is not by any means the only one. What lies beyond this world are other spatio-temporal realms, inaccessible from this one, perhaps evolving under different laws, but equally a part of nature in its entirety. So naturalists must allow that nature comprises this spatio-temporal world together with all other realms required by the best scientific explanations of this one.

Naturalism as Method and as Ontology

Because specifying what nature is brings in reference to scientific explanation in this way, naturalism is sometimes regarded as a rule of method rather than a metaphysical doctrine. There is a natural method of inquiry, which consists in setting out to explain and understand the world by finding the natural causal processes by which natural objects come into being, produce their effects, and pass away. All genuine knowledge is of this natural, experimental kind; human beings, themselves part of the natural order, have no special insight or intuition that could provide a more direct path to knowledge. And the methods of the natural sciences, which are so successful, are these natural methods refined and made more systematic.

If naturalism is in this way a matter of method in inquiry, the natural world is the world revealed by the methods of the natural sciences. This does not, in itself, place many constraints on what sort of world that might be: One cannot tell in advance what the scientific method might reveal. Maybe it will uncover not just familiar items—ships and shoes and sealing wax, for instance—but fire-breathing dragons, the Fountain of Youth, or the Philosopher's Stone. Naturalism regarded as a method maintains that ontology should be developed a posteriori—whatever is vindicated by the sciences is acceptable, whatever is not, is not.

The attempts made during the twentieth century to establish the existence of the paranormal phenomena (telepathy, precognition, and telekinesis) illustrate this approach. The methods adopted were naturalistic methods, which in themselves set no limits to what can exist.

A more affirmative naturalism goes rather further: It claims not only that the scientific method provides the only sound basis for knowledge of reality, but also that it has already established that all nature has a physical basis. The fundamental causal network consists in chains of physical cause and physical effect, produced by the operation of physical forces. All realities have at least a physical nature of this kind, whatever else may prove to be true of them. This leaning toward a physical basis for everything has been encouraged by the development of more and more sophisticated instruments for probing the observable, tangible, and manipulable world of matter, and of increasingly successful physical theories to account for what is discovered.

Yet this tendency to regard physics and chemistry as the basic and comprehensive sciences does not in itself require a materialistic ontology. Physicalism is a particularly stringent version of naturalism. A physical basis for everything does not rule out other characteristics. It is possible to affirm naturalism while insisting that the higher faculties in humans and other animals cannot be given a physicalistic reduction, and nonmaterialistic naturalism avoids the difficulties that materialism has, for example, in accounting for the intensional characteristics, such as linguistic meaning and psychological understanding.

The Case for Naturalism

Bertrand Russell was once charged, as Hamlet had charged Horatio, that there are more things in heaven and earth than were dreamt of in his philosophy. He retorted that he preferred it to be that way, rather than the other way around. He thus expressed the naturalist attitude, which is imbued with the spirit of Ockham's Razor: Extravagance in ontology is to be avoided. We must recognize the reality of what most plainly exists, the familiar natural world in which we live and move, and have our being. Beyond that, one should be cautious. There is no compelling evidence, of any kind, that there is more to reality than the nature revealed by scientific investigation. So the rational position to adopt is the economical, minimalist one that there are no further realms.

the eleatic argument

The Eleatic Stranger in Plato's Sophist proposes that "Power is the mark of Being"—that the true test of reality is to be efficacious. That which is real makes a difference, changes things, has effects. The outcome of a serious and sustained inquiry into what actually passes this test, is naturalism. For whatever operates in such a way as to alter the course of nature belongs by that very fact to the causal network of the natural world. And whatever has no such impact has no claim to reality.

The Eleatic argument is perhaps even more powerful as a methodological one: The only way in which anything can call attention to itself, and so stake a claim to reality, is by having an effect, either directly, in perception, or indirectly, through the traces it leaves in instruments. Without any such impact, there can be no reason to suppose that the thing in question exists. And that which there is no reason to think exists, should have no place in any ontology.

This argument needs to be elaborated to cover purely theoretical reasons for admitting other realms—parallel universes, for example, or sets to underpin mathematics. It is then not so straightforward to exclude higher realms, with unmoved movers, divine providences, or guardian angels. Here the argument must be that, unlike the extra worlds of quantum theory, these other worlds have no essential link to the natural explanation of what occurs in this one.

the self-correcting vindication

Naturalism should be adopted as the proper stance in philosophy, just because it is open to development. Wherever the current conception of the world of nature is inadequate, this deficiency is likely, sooner or later, to be revealed, for there will be unaccountable phenomena that need to be accounted for. Current explanatory resources having proved inadequate, they must be expanded. New entities, properties, or forces must be recognized. The ontology of naturalism will grow to whatever extent the facts require, no more, but no less. So naturalism will always be the best philosophical stance. To maintain this position, a naturalist must show that explanatory reasoning does not advance in this way from the natural to the supernatural.

These three lines of support for naturalism all rest on a negative base: the claim that there is no valid method of discovery beyond those used in the natural sciences. So a thorough naturalism must explore, and reject, a priori reasoning in natural theology, and the claims of religious experience to provide knowledge of a transcendent divinity. It must also argue that the hermeneutic method of some social sciences, and the empathy by which humans reach a commonsense understanding of one another, does not involve entities or processes beyond those revealed by naturalistic methods.

The Implications of Naturalism

In general, naturalism and religion are at odds with one another. Most religions posit powerful and purposeful supernatural forces, responsible for creating the natural world, for shaping its progress, and for determining the destinies of its inhabitants. These beliefs are not compatible with the naturalistic outlook. This does not, however, preclude a religious attitude accompanying naturalism, involving feelings of awe and wonder toward the natural realm, and impulses to value and care for it. Nor does it rule out a pantheism such as Benedict de Spinoza's. Spinoza identified God with Nature, insisting, as naturalists do, that there is nothing beyond this law-governed world. The atheistic varieties of Buddhism, in which this world is the only one, and where law governs the world's unfolding, would also be naturalistic religions if they were to accord independent reality to the material realm.

Naturalism requires that religious experience, and in particular mystical experience, be given a reductionist interpretation. Such experiences are regarded as unusual states of mind that have their own causes and consequences within the natural world, but do not provide any contact with, or insight into, a supernatural realm.

metaphysical idealism

Naturalism takes its cue from the natural sciences, and with the exception of some more fanciful interpretations of the measurement paradoxes in quantum theory, the sciences are resolutely realist about the material world. Realism maintains that the world of nature is as it is, irrespective of any human opinions about it. The natural world is not dependent on, or brought into being by human mind, will, or experience. As this is the working philosophy of the natural sciences, it is difficult to combine naturalism with metaphysical idealism, which implies that matter is in some way a function or aspect of mind.

A thorough-going phenomenalism, such as an atheistic version of George Berkeley's philosophy, might be thought to count as an idealistic naturalism in which every object of experience does indeed belong to a law-governed spatio-temporal world, but where to be spatio-temporal is to have a derivative status, with perceptual experiences as the basic elements out of which it is constructed.

However, such a view places the experiencing mind outside the world of nature, and this puts it in conflict with one of the most profound aspects of naturalism, the view that the human species enjoys no specially privileged position in the scheme of things. Naturalism implies that human beings share with all other beings a common status, as contingent, temporary configurations in the law-governed natural world. The human world is a part of the natural realm, not a distinct cultural sphere to be contrasted with it.

Realist naturalism takes the Earth and its living inhabitants as genuine independent realities, and by locating the human race within the natural world, can make progress toward explaining how it came into being, and how humans came to have the epistemic and cognitive capacities that they do. Not even the more objective post-Hegelian metaphysical idealisms can provide any basis for an explanation of how humans came to be as they are.

the problem of universals

Realists about universals—properties and relations—divide into the Platonists, who allow the real existence of properties even where there is nothing in this world that instantiates them, and Aristotelians, who admit the reality of instantiated universals only. Plato's heaven, a higher realm containing perfect patterns for the properties imperfectly realized here below, is clearly incompatible with naturalism, and it seems probable that unless they can be vindicated as being required for explanations of what happens in this world, no system that admits uninstantiated universals can be naturalistic. Nominalist accounts of properties do not face any problem so far as naturalism is concerned.

determinism

Although naturalism stresses that it is by natural processes, involving natural causes only, that anything at all occurs, it is not committed to an absolute determinism. If there are causes at work, they are natural ones, but there may not be a cause in every case. There has to be at least enough general order in the world for it to provide an environment suitable for life and consciousness, but that admits of exceptions, here and there, to every rule. Quantum theory is not fully deterministic, as its causal relations are probabilistic. Naturalism requires there to be at least as much causality and law in the world as the development of natural sciences calls for, but it does not require any more than that.

mathematics and logic

Naturalism is almost bound to take a reductionist view of the so-called abstract objects of mathematics and logic—their numbers, functions, and relations. For the number twenty-seven, or the square root of negative one, or the relation of contrariety seem to fail both the spatio-temporal location test, and the Eleatic causal power test for natural reality. W.V.O. Quine, who was very much of a naturalistic bent, found himself forced to accept the reality of sets as a foundation for mathematics, something essential for physics, which provides the best description of the world. So sets, although not themselves naturalistic beings, have a place in the best ontology. This is a departure from pure naturalism. Hartry Field (1980), among others, has attempted to develop a philosophy of mathematics that dispenses with numbers or other mathematical objects.

The situation with the objects of geometry seems less problematic. If space-time is taken realistically (not, as with G.W. Leibniz, as a mere system of relations among physical objects), then the objects of geometry (points, lines, shapes, and geometrical solids) can be given a naturalistic home as aspects or parts of space-time.

Modality

The natural world comprises not only objects and the properties they actually possess. It includes what might be, yet is not (natural possibility), and what not only is but must, in the course of nature, come to pass (natural necessity). To meet this situation, the properties that things now actually possess (categorical properties) must be distinguished from those that provide the basis on which things will change and develop (dispositional properties or powers). Aristotle and the medieval Aristotelians such as Thomas Aquinas introduced potentiality (in contrast with act ) to specify what an object is capable of—its range of possibilities. The modern version of this is the specification of an object's powers. The power to become F is a different property from being F, but it is itself a real categorical property, perhaps some feature of the underlying fine structure of the object that possesses it.

The powers that there are in the world determine and explain what is naturally possible, should they be exercised. And where they are exercised, the powers are bound to act as they do and produce their effects. This situation is therefore one of natural necessity.

Beyond natural possibility and necessity, however, lie that which is logically possible, even though ruled out by the laws of nature (such as a ball thrown into the air and just remaining there), and that which is, not just naturally, but logically necessary or impossible. Some philosophers treat possibility and necessity by introducing possible worlds, worlds in some way additional to the one actual world. This at least seems to be a departure from naturalism because additional, merely possible worlds do not belong in the same causal network with this world, and thus fail the Eleatic test on which naturalism insists.

Naturalism therefore seems to be committed to providing an account of the logical modalities that does not involve any special ontological commitments. The proposal that logical necessity is a reflection of language, of meaning and use, was an attempt to provide such an account. The linguistic theory has fallen out of favor; more recent accounts attempt to construct possible worlds from appropriately selected sets—sets of descriptions, or unactualized recombinations of elements from the actual world. These are accounts in terms of ersatz possible worlds. Provided a naturalistic account of sets can be given, such proposals would be naturalistic theories of necessity.

Objective Morality

Morality is another problematic area for naturalism. The standard naturalistic characteristics are the contingent factual actualities, and these do not include in any straightforward way the values that objects or situations may have. The size and shape of an object enters into the natural causal nexus, but its goodness does not seem to. A naturalistic account of morality must find a place for good and evil, but not in the inherent structure of the world, as a fully objective moral realism does. Nor can naturalism ground moral law in the commands of a deity. It must explain right and wrong, good and evil, as arising in the nature, preferences, or reactions of people, and in the structure of the societies within which people live out their lives. Whether an account of morality along these lines can satisfactorily explain the authority and impersonal binding force that moral imperatives seem to possess, is perhaps the most difficult issue for naturalist theories of morality.