Epiphenomenalism: One of philosophy’s most disturbing ideas

This article was first published on Big Think in September 2022. It was updated in March 2025.

What if you don’t matter? What if all of your thoughts, precious feelings, great dreams, and terrible fears are completely, utterly, spectacularly irrelevant? Might it be that all of your mental life is just some pointless spectator, looking on as your body does the important stuff of keeping you alive and running about? What actually is the point of a thought?

This is the view of “epiphenomenalism,” and it might just be one of the most disturbing ideas in all of philosophy.

The pointless chiming of the clock

On any given day, we will make thousands of decisions and perform countless actions. We will move our legs to walk, open our mouths to eat, smile at our friends, kiss our loved ones, and so on. Today, we know enough about neuroscience and physiology to give a complete and full account of how this happens. We can point to the parts of the brain that activate, the route the nerve signals will take up and down the body, the way the muscles will contract, and how the body will react. We can, in short, give a full physical account of everything we do.

The question, then, is: what is the point of our consciousness? If we can explain all of our behavior quite happily (or “sufficiently” as philosophers like to say) with physical causes, what is there left for our thoughts to do?

Anthropologist Thomas Huxley argued that our thoughts are a bit like a clock’s chime at the hour. It makes a sound, but it makes no difference at all to the time. Likewise, our thoughts and subjective feelings might be very nice and appear very special to us, but they are completely uninvolved.

The problem of mind-body dualism

This all stems from a key problem of dualism, which is the philosophical idea that the mind and body are different things. There is something intuitive to the idea. When I imagine a flying dragon with fiery breath and leathery wings, that is entirely different from the physical world of lizards, candles, and bats. Or, put another way, you cannot touch with your finger or cut with a knife the stuff that happens in your head. But we don’t like believing that our thoughts don’t exist. So, what are they?

The problem in dualism is understanding how something mental, nonphysical, and subjective possibly could affect the physical world and especially my physical body. Yet, it clearly happens. For instance, if I want a cupcake, I make my hand move toward it.

So, how can the immaterial affect the material? This “problem of causal interaction” is not easily resolved, and so some philosophers prefer the epiphenomenalist response, “Perhaps our minds don’t do anything.” If we want to retain the idea that our minds exist but in a completely different way as the physical world, then it might be more palatable to jettison the idea that they do anything at all.

Integrated information theory

Then, what is the point of consciousness? There are some, such as neuroscientist Daniel De Haan and philosophers Giulio Tononi and Peter Godfrey-Smith, who argue that consciousness can best be explained by “integrated information theory.”

In this theory, consciousness is something that emerges from the sum of our cognitive processes — or, more specifically, the “capacity of a system to integrate information,” as Tononi writes. In other words, consciousness is a net product of all the other things our mind is doing, such as synchronizing sensory inputs, focusing on specific objects, accessing various types of memory, and so on. The mind is an overseer at the center of a huge web and is the result or byproduct of all the incredibly complex things it needs to do.

But this kind of “emergentist” theory (since the mind “emerges” from its operations) does leave us with some epiphenomenal questions. It seems to suggest that the mind does exist but that it can be fully explained and accounted for by other physical processes. For instance, if we suppose our consciousness is the product of our complex and various sensory inputs, as Godfrey-Smith offers, then what does conscious thought actually add to the equation that our sight, smell, interoception, and so on are not already doing? By analogy, if a “traffic jam” is just the term for a collection of stationary cars and trucks, what does the concept “traffic jam” add that all those vehicles don’t already provide? A traffic jam has no causal role to play.

This is not to say that consciousness is a mistake or without value. After all, without it, I would not be me and you would not be you. Pleasure would not exist. There would be no world at all. We cannot even imagine a life without consciousness. And epiphenomenalism does believe that physical events, like our synaptic sparks and neuronal interactions, do cause our mental events.

But if epiphenomenalism is correct, it means that our thoughts don’t add anything to the physical world that isn’t already ongoing. It means that we are locked in our heads. All the thoughts and feelings are ultimately pointless or nonsense. We are like children pretending to drive a car — it can be great fun, but we are really not in charge.