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Can the “Physical World” Be Wholly Physical? Physical at All?

Nothing ever physically touches anything else in the physical world, yet the effects of objects on each other are a constant occurrence

Sounds like the answer should be “Of course!” But the question may not be as simple as it appears.

Let’s wind the clock back to the first century BC, when a Roman poet and philosopher named Lucretius wrote the poem On the Nature of Things.” In this poem, Lucretius outlines a philosophy known as Epicureanism in order to demonstrate the world can be explained without reference to a deity. In the Epicurean philosophy, only three things exist: atoms, the void, and the universe. Consequently, everything we see in the physical world can be reduced to atoms bumping into each other.

Titus Lucretius Carus (ca. 99 BC – ca. 55 BC) — a Roman poet and philosopher

You may notice that Epicurean philosophy sounds similar to modern day physics. This is not an accident. Through the influence of chemist Robert Boyle (1627–1691) and the Royal Society, the view, directly derived from Epicurean philosophy, that the physical world could be reduced to atoms became the dominant view. However, the moderns made different assumptions about atoms. They did not consider them eternal, for example, as Lucretius did.

So, why does Epicureanism claim that the only things that can exist are atoms bumping into each other?” As he explains it, it sounds like common sense reasoning. First of all, in everyday life, we see that physical objects, for the most part, only interact through touching each other. Additionally, the interaction of objects without any kind of contact is hard to explain physically.

How can the information necessary for the interaction flow from one object to the other without any kind of physical contact? The necessary conclusion is the information must be transmitted through a non-physical means, which is obviously at odds with a purely physical explanation of the physical world. Therefore, Lucretius logically concluded the only kinds of physical interactions that can take place are atoms bumping into each other.

You may notice a problem. It is a very big problem. We now know that the physical world consists of more than atoms bumping into each other. There is energy. There is gravity. There is magnetism. There are electrical fields. None of these physical phenomena can be reduced to atoms bumping into each other.

In fact, atoms do not even bump into each other. Instead, they are repulsed by field effects. Nothing ever physically touches anything else in the physical world.

Let’s return to Epicureanism. As we saw, the reasoning seemed very logical. The information relevant for physical interactions can only be transmitted physically by touching. We now know that nothing ever physically touches. Applying the logical rule of modus tollens (for example, “if being the king implies having a crown, not having a crown implies not being the king”), we must therefore conclude, if we follow Epicurean logic, that all physical interaction proceeds by non-physical information transmission.

Consequently, an Epicurean such as Lucretius, when faced with modern scientific evidence, would be forced to the very counterintuitive conclusion the operations of the physical world are almost entirely non-physical!

So, if asked our opening question, a modern Epicurean must answer with a resounding “No!” Which is probably not the place he intended to be…

You may also wish to read: Why physicalism is failing as the accepted approach to science. The argument that everything in nature can be reduced to physics was killed by the philosophical Zombie, as Prudence Louise explains. Physicalism which depends on a mechanistic view of the universe, was challenged by observer-dependent quantum mechanics. Then the Zombie started walking…

Eric Holloway

Senior Fellow, Walter Bradley Center for Natural & Artificial Intelligence
Eric Holloway is a Senior Fellow with the Walter Bradley Center for Natural & Artificial Intelligence, and holds a PhD in Electrical & Computer Engineering from Baylor University. A Captain in the United States Air Force, he served in the US and Afghanistan. He is the co-editor of Naturalism and Its Alternatives in Scientific Methodologies.

Can the “Physical World” Be Wholly Physical? Physical at All?