“I only believe what I can see.” This belief is everywhere, and is called “Physicalism.” Last week I discussed ways it shows up in our culture, and some of the disastrous consequences. This week I offer one of three reasons why Physicalism is not rational.

If It Is True, It is False

In short, if Physicalism is true, it must be false. It is what is known in logic as a “self-defeating” view. No matter what else can be said in favor of Physicalism, this is a fatal flaw that puts the view to death even before it can mount arguments in its defense. This objection is made by Christians and non-Christians alike, as it is simply the application of logical principles to the core belief of Physicalism.

Understanding Self-Affirming and Self-Defeating Statements and Beliefs

To understand this argument against Physicalism it is important to first understand what self-affirming and self-defeating beliefs are. To do so we must discuss statements, as statements are what express beliefs. So if it can be shown a statement is self-defeating, the corresponding belief is self-defeating as well.

As you may remember from English class, all statements are about something (they have a subject). “Lori is compassionate” is a statement about Lori. It identifies a virtue (compassion), which is true of her.

Sometimes the subject of a statement includes the statement itself (the statement itself falls into the statement’s “scope of reference”). For instance, “All sentences are composed of words.” The subject of this sentence is “all sentences.” Of course, the sentence making this claim is itself a sentence. So it falls within its scope of reference.

In cases like this we have to ask, “Does this statement meet its own criteria?” Is what it says about all statements also true of this very statement? In this case it does. The statement is that all sentences are composed of words. This is a sentence—is it composed of words. It meets its own criterion. So it is self-affirming.

Another example of a statement that includes itself in its scope of reference is “Every idea should be carefully analyzed.” The idea that “every idea should be carefully analyzed” is itself an idea. So the subject here again falls into its’ own scope of reference. Does it meet its own criteria? Is it self-affirming? It is. This very idea, like all others, should be carefully analyzed.

Here’s another example: “All sentences contain no more than four words.” Again, this sentence is within the scope of reference of the subject “all sentences.” But does it meet its own criteria for truth the statement sets out? No—this sentence has eight words. Therefore it is not self-affirming. Rather, it is self-defeating. It is false. The only way the statement could be true is if the statement were false—that not all sentence contained no more than four words. But in that case it would already be false!

Applied to Physicalism—It Is Self-defeating (if True, then False)

Let’s now apply this to Physicalism. Physicalism claims that, “Only physical things exist.” The subject of this statement is “physical things” and the predicate is “exist.” But this belief (“that only physical things exist”) is itself a thing that is believed to exist—to be real, true, and accurate. This belief itself is within the statement’s scope of reference. So is it physical? Does this belief itself meet its own condition for existence? No, it doesn’t. Beliefs are not physical things. You cannot hold them in your hand. They do not have an odor. They don’t weigh so many pounds. They are not green. You can’t get them under a microscope to determine their molecular makeup or get them in a test tube to see how they react to various chemicals.

Therefore, the belief that only physical things exist is self-defeating. If only physical things exist, one can not logically affirm the immaterial belief that “only physical things exist.” To be consistent one would have to claim that the belief “only physical things exist” is not real/true/accurate (and therefore logically the opposite is true—that non-physical things also exist, namely this belief). But in that case one is denying that only physical things exist—is affirming that non-physical things exist.

The Physicalist has no way out. It is a classic case of a statement (and embodied belief) that is self-defeating, and therefore false. By the way, for fun “test” these other often-heard beliefs to see if they meet their own criteria or are also self-defeating and therefore false:

• “I only believe what I can see with my own two eyes.”
• “There are no truths.”
• “All truth is relative.”
• “Language cannot convey meaning.”
• “All generalizations are false.”
• “All morality is relative, so you should be more tolerant.”

Conclusion

Nothing else needs to be said about Physicalism—it can’t be true! It doesn’t even get out of the starting gate, logically speaking. The only way for it to be true is for it to be false. It is self-defeating.

Yet much more can be said in critique of Physicalism. Next week I’ll discuss a second problem it runs into (a topic near and dear to my heart, which I wrote my dissertation on).

Until next week, grace and peace.

For further reading I suggest Love Your God With All Your Mind: The Role of Reason in The Life of The Soul, Chapter Five: “Clearing the Cobwebs from Our Mental Attics.” For more a more detailed treatment of logic, see Philosophical Foundations for a Christian Worldview, Chapter Two: “Argumentation and Logic.”