Over the last year (or two?), I’ve had on-again and off-again exchanges on various blogs with reader “Crude” about the definition of metaphysical naturalism. I’d like to comment on his (?) recent objections in the combox on Victor Reppert’s blog start with the linked comment here and work your way down. Each time we’ve had an exchange, I’ve (virtually speaking) walked away scratching my head, not feeling the force of Crude’s objections. Since that could be due to a misunderstanding on my part, I’d like to formally state that I consider my views on these matters to be tentative and a work in progress. In other words, I’m publishing the post in the spirit of truth and learning, not in an attempt to try to score “debate points.” I hope this post (and his responses) will help to advance the discussion.*

* I’m referring to Crude as a “he” but I don’t know if that’s the correct pronoun. Crude can correct me on that also if I’m wrong.

Definitions

First, let’s start with my definitions, which are almost entirely taken from the writings of Paul Draper.

physical entity: an entity which is either (1) the kind of entity studied by physicists or chemists today; or (2) the kind of entity studied by physicists or chemists in the future, which has some sort of nomological or historical connection to the kinds of entities studied by physicists or chemists today.

causally reducible: X is causally reducible to Y just in case X’s causal powers are entirely explainable in terms of the causal powers of Y.

ontologically reducible: X is ontologically reducible to Y just in case X is nothing but a collection of Ys organized in a certain way.

natural entity: an entity which is either a physical entity or an entity that is ontologically or causally reducible to a physical entity.

nature: the spatio-temporal universe of natural entities.

physical world: equivalent to “nature.” Notice that the physical world, if it exists, is a public, objective world, in contrast to the mental world (see below).

mental world: a private, subjective world of conscious experiences like thoughts, feelings, imaginings and sensations

supernatural person: a person that is not part of nature but can affect nature. Examples of supernatural persons include God, angels, Satan, demons, ghosts, etc.

metaphysical naturalism (hereafter, “MN”): the hypothesis that the universe is a closed system, which means that nothing that is not part of the natural world affects it. MN has three implications.

(1) MN entails the non-existence of all supernatural persons, including God, and so entails atheism.

(2) MN entails that nature causally explains the existence (or, making room for eliminative physicalists, the apparent existence) of the mental world. In other words, MN entails that natural entities are ontologically fundamental.

(3) MN entails that nature does not have a teleological or purposive explanation.

scientific naturalism (hereafter, “SN”): a form of MN which holds that the explanation in question is a scientific one (and in particular a covering law explanation). Of course, scientific naturalists don’t know exactly what that explanation is. They don’t know what the laws are that explain why matter, when arranged in a certain way (e.g. in the form of a functioning nervous system), brings mind (or apparent mind) into existence. But scientific naturalists must hold that there are such laws.

eliminative physicalism: a form of SN which holds that the mental world doesn’t exist.

eliminative idealism: the view that the physical world doesn’t exist.

metaphysical supernaturalism (hereafter, “MS”): the hypothesis that the physical world (or, making room for eliminative idealists, its appearance) is a product of one or more non-physical mental entities. In other words, MS entails that mental entities are ontologically fundamental.

personal supernaturalism (hereafter, “PS”): a form of MS which holds that the mental entities in question are persons and that the explanation of the physical world is teleological or purposive. Of course, personal supernaturalists need not claim to know what purposes were being pursued when the physical world (or apparent physical world) was created; but they must hold that there are such purposes.

metaphysical deism (aka “deistic supernaturalism” or simply “deism”): a form of PS which identifies the mental reality responsible for the existence of physical reality with a supernatural person who created the natural world but does not act in it and is not worthy of worship. (To say that God acts “in the natural word” is to say that, in addition to creating and/or sustaining the world, God intentionally brings about particular natural effects involving God’s creatures or other parts of nature.)

metaphysical theism (aka “theistic supernaturalism” or simply “theism,” hereafter, “T”): a form of PS which identifies the mental reality responsible for the existence of physical reality with God—in other words, with a unique person who is omnipotent and omniscient and thus, lacking non-rational desires, omnibenevolent as well.

metaphysical atheism: the belief that T is false.

otherism (hereafter, “O”): a catch-all category for all hypotheses which are incompatible with both MN and MS

pansychism (hereafter, “P”): a form of otherism which holds that concrete reality consists of a single sort of “stuff” that essentially has both physical and mental aspects.

Objections

As I understand him (?), here are Crude’s objections.

(1) Regarding the definition of “physical entity,” this leaves the definition of MN open-ended. In Crude’s words, “Having some kind of historical/nomological connection to what we study today’ is absurdly open-ended and lets all of the usual problems obtain.”

(2) Regarding the definition of MN, MN is logically compatible with things we normally regard as logically incompatible with atheism. In Crude’s words, “When we see the list of theisms on offer (polytheism of the sort that involves Zeus, etc, would swing right against it – those gods were apparently physical beings).”

(3) Regarding the definition of “supernatural person,” I will quote Crude at length:

And we’re right on back to various problems. For one, whether these things are or aren’t part of nature depends on the attention and scope of physicists and chemists, which itself is a tremendously slippery standard to make use of since it inevitably is tied up in social considerations. Were angels and God ‘natural’ in Newton’s time?

And all of this ignores the historical views that were problematic here – everything from quantum effects to action at a distance to otherwise, at one point historically, could have easily been put into the ‘supernatural’ pile. Multiverses? Measurement problems? Supposed waveform ‘collapse’ in general? Action at a distance? Universes being created, period? Weird stuff that sure ran contrary to our views of what nature was defined as or supposed to be. So we just kept changing the definition of nature.

To that end, I think, the damage is done – this is a historical problem, a set of shifts of understanding that has already taken place, and will likely take place again.

Response

Let’s consider each of Crude’s objections in turn.

First, what about (1)? It’s not exactly clear what Crude takes this objection to mean. Take the statement, “Physical entities exist.” What is the problem?

(a) Perhaps he (?) means that the statement is non-cognitive, i.e., that it does not express a proposition. This seems false, however, since it seems that the statement has a truth value, i.e., it’s either true or false.

(b) Perhaps Crude’s complaint is that the scope of the statement is dynamic, i.e., it can change over time in the light of new scientific discoveries. There is truth in that statement. Suppose that in the year 2015 physicists revise the Standard Model to include a new type of elementary particle called the darkoton which accounts for the presence of so-called “dark matter.” But such a discovery would pose no problem because it would be nomologically and historically connected to the kinds of entities which physicsts study today. Crude would probably say, ” I agree, but that’s not the kind of discovery I was talking about.”

Since I don’t want to attack a straw man, I’ll defer to Crude to provide an example of a hypothetical discovery which he claims makes MN open-ended in a problematic way. What I want to emphasize here is two-fold. First, MN is falsifiable: there’s a limit to the kinds of discoveries which are compatible with MN. If “nature” ultimately has a teleological or purposive explanation, then MN is false. And so any evidence of a cosmic telos or purpose is, accordingly, evidence against MN; the definition of MN cannot be revised or expanded to include it. Or so it seems to me; again, I’ll defer to Crude to explain why he (?) disagrees.

Second, the track record of naturalistic explanations gives us a strong reason to expect that future scientific discoveries will not appeal to supernatural agents like gods, ghosts, souls, vital forces, etc.

Let’s turn to (2). I used to study Greek mythology when I was younger and so I consider myself decently well-informed about it. Such beings as the Greek gods are logically incompatible with MN. As I understand Greek mythology, the Greek gods were conceived to be physical beings in the same way that the second person of the Trinity was/is conceived to be a physical being: by being incarnated. Their supernatural powers did not derive from their physical body or the laws of nature. So, while various polytheisms may have held that various gods did take physical form, it hardly follows that such gods were nothing but physical entities. All that follows is this: their physical forms were physical entities, but the gods themselves were much more than their physical forms. In short, (2) is a very weak objection.

Finally, consider (3). This can be easily dispensed with because this objection  just ignores the part of the definition of “natural entity” which refers to what physicists and chemists study today.

Related Resources

“Defining the Supernatural” by Richard Carrier