There are two main kinds of naturalism: materialism and pluralistic naturalism. Materialism, or physicalism, is a "monistic" form of naturalism in that it maintains that only one basic kind of stuff exists--physical stuff. Pluralistic naturalism, by contrast, combines naturalism with ontological pluralism, the idea that there is more than just one basic kind of stuff. Thus while materialists reject the reality of (irreducibly) nonphysical stuff, pluralists affirm the existence of at least one kind of (irreducibly) nonphysical stuff.
Our mental traits might be (irreducibly) nonphysical properties of the brain. But since such property dualism is compatible with the idea that there are only physical substances, it is compatible with both materialism and pluralism. Where materialism and pluralistic naturalism seem to diverge is in denying or affirming, respectively, the existence of nonphysical abstract objects, transcendent Platonic forms beyond nature.
This sort of pluralistic naturalism maintains that in addition to physical objects and their (physical and possibly nonphysical) properties, there are transcendent abstract objects (such as numbers) and their abstract properties (such as being prime numbers) subsisting within a Platonic realm outside of space and time. Such "Platonic realism" is motivated by the fact that the number 4, for instance, does not seem to be the sort of thing that can be located at a particular point in space, nor the sort of thing that can come into or go out of existence at a particular time. Instead, abstract entities at least appear to be universal and timeless Platonic forms. If real, Platonic forms exist even if no one has ever perceived them, and they do not cause changes in either physical objects or human minds because they lack spatiotemporal location and never change (the number 4 can never become an odd number, for instance). So long as Platonic abstract objects are acausal, they are compatible with naturalism because, although they transcend nature, they do not intervene into it to bring about changes in nature.
There are also alternative conceptions of abstracta compatible with materialism: (1) that they do not exist at all (nominalism); (2) that they only "exist" in minds (conceptualism, which treats abstract objects as illusions in the same way that George Berkeley's idealism treats physical objects as illusions); and (3) that they really do exist as universals, but are embodied within all physical objects (Aristotelian realism, or moderate realism) instead of existing apart from and being "mirrored" by them.
In principle, pluralism allows the possibility of physical stuff, mental stuff, and abstract stuff, with each truly distinct from the other. But at the very least there is tension, if not outright incompatibility, between naturalism and interactionist substance dualism, the notion that there are distinct mental substances that interact with the physical world. For the idea of an at bottom nonphysical substance that can cause physical changes comes awfully close to the notion of a supernatural cause. In The Cambridge Companion to Atheism Evan Fales suggests that naturalism minimally requires that "if there are immaterial mental substances, they cannot be things that exist apart from embodiment in a physical substance" (p. 128), for disembodied agents like gods and souls are prime examples of supernatural beings.
Finally, it should be noted that pluralism is technically broader than the pluralistic naturalism discussed here. Because any position maintaining that there is more than just one kind of thing is pluralistic, any theism affirming that both God and the physical world exist would be a form of pluralism.
The Craig-Washington Debate: Does God Exist? (1995) [ Index ]
An annotated transcript of an oral debate held at the University of Washington in 1995 on the existence of God. Craig's case for theism included the argument from abstract objects, the kalam cosmological argument, the argument to the fine-tuning of the universe, the moral argument, the resurrection of Jesus, and religious experience. Washington cited abstract objects and harm (read: evil) as evidence for the nonexistence of God.
This is a rebuttal of Rea's claim that naturalism "is without rational foundation." This essay shows that adopting the "research program" of basic empiricism is universally appealing, and since naturalism as a "worldview" follows from adopting basic empiricism and applying it to the facts of the world, naturalism has a rational foundation. Rea's conclusion that naturalism must abandon materialism and realism about material objects and other minds because naturalism cannot "discover" intrinsic modal properties is also disproved.
In the first part of this essay Augustine discusses what naturalism entails for one's ontology, considers various ideas about how to define the categories "natural" and "nonnatural," and develops criteria for identifying a potentially supernatural event. In part 2 he presents a persuasive empirical case for naturalism based on the lack of uncontroversial evidence for any potential instances of supernatural causation, particularly in our modern scientific account of the history of the universe and in modern parapsychological research.
The Drange-Wilson Debate (1999) [ Index ]
An Internet exchange between Theodore Drange (philosophy professor at West Virginia University) and Douglas Wilson, in which the two debate the topic, "The Arguments from Nonbelief and Confusion for the Nonexistence of God vs. The Transcendental Argument for God's Existence."
Citing both philosophical considerations and modern day physics, Smith argues that "it is nomologically necessary that a beginningless universe has an internal causal explanation (be it deterministic or probabilistic) but no external causal explanation."
According to a form of the kalam cosmological argument expounded by William Lane Craig, there cannot be a beginningless temporal world because the application of Cantorian set theory of transfinite arithmetic to the real world generates counterintuitive absurdities, thereby disclosing that an infinite set of real entities is metaphysically impossible. This article shows how this is not the case by pursuing a novel approach wherein it is understood that an infinite set of real entities is not a set, considered as a technical term of art, within the meaning of Cantorian theory. Upon accepting the original version for publication, Quentin Smith, then editor of Philo, wrote: "Your paper has been studied thoroughly for some time and there is agreement that it is at least an undercutting defeater of [William Lane] Craig's beliefs about real infinites, probably even an overriding defeater. More importantly, it introduces a novel metaphysical theory of the relation of transfinite arithmetic to concrete reality." Guminski's persuasive challenge to Craig's account of why Cantorian transfinite arithmetic should not be deemed to apply to the world of concrete entities has yet to be answered by Craig. The world wonders.
Arnold T. Guminski's "The Kalam Cosmological Argument: The Question of the Metaphysical Possibility of an Infinite Set of Real Entities" showed that the argument by William Lane Craig and others that real infinites are metaphysically impossible presupposes the standard version (SV) of how Cantorian set theory presumably applies to the real world. This is the case because it is the application of SV to the real world which generates counterintuitive absurdities. However, there Guminski also showed that there is an alternative version (AV) of applying Cantorian set theory to the real world, the application of which does not generate counterintuitive absurdities. In the present paper he shows that given AV, an infinite temporal series is metaphysically possible, producing a result that should be equally satisfying to both theists and nontheists who are loath to believe that a beginningless temporal world is metaphysically impossible. However much theists and nontheists may disagree about other issues, they are at least able to agree upon one important thing: the kalam cosmological argument fails insofar as it is grounded upon the alleged metaphysical impossibility of an infinite temporal series.
Graham Oppy provides a "general ground" for rejecting all modal theistic arguments, arguments for the existence of God which make use of the premise that God is a being who exists in every possible world, focusing on the arguments of Alvin Plantinga and Brian Leftow for illustrative purposes.
The editors of this collection claim that its essays aim to: (1) show that naturalism "fails to deal adequately with a number of desiderata"; (2) establish that a "consistent" naturalism must be a strong form of reductive physicalism; and (3) showcase "the contemporary resurgence of philosophical theism." While the volume clearly accomplishes the third objective, it doesn't get anywhere near accomplishing either of the other objectives.
Smith reviews Swinburne's book, Is There a God?
Theism or Atheism: The Krueger-McHugh Debate (2003) [ Index ]
This is a written debate which was originally conducted online and organized by Internet Infidels.