Tuesday, December 29, 2009

Duex Ex Homo Sapiens

I just finished reading an excellent book, “Supersense: Why We Believe in the Unbelievable” by Bruce Hood. The book explores how the way our minds are wired leads us to intuit the supernatural. It’s concepts such as the ones in this book, the way our minds really work as opposed to our intuitive understanding of how our minds work, that kept me interested in psychology in college.

Among other things the book discusses “essentialism,” the tendency we all have to think that there is a metaphysical essence attached to all objects and organisms that makes them what they are. The idea of essences goes all the way back to ancient Greek philosophy, and Dr. Hood quotes a Greek philosopher to make his point. He tells the story of the Ship of Theseus, a famous ship in the Greek world which saw years of service. Over its lifetime, parts of the ship were replaced as they became warped or rotten. Was it still the same ship at the end of its service as it had been at the beginning, despite having had many of its planks replaced? What if one were to take the cast-off planks and assemble them into a second ship? Which would be the real Ship of Theseus, the one that had parts slowly replaced, or the one that was made of the original, now cast-off planks?

A modern-day Ship of Theseus lies at anchor in Boston Harbor. The USS Constitution is an eighteenth-century wooden super-frigate, and is the oldest ship in the world to hold a continuous naval commission. Built during the “pseudo-war” between the United States and France near the end of the1700s, it became famous during the War of 1812 when its crew watched shot from the British frigate HMS Guerriere bounce off its sides and gave it the nickname, “Old Ironsides.” In the over two centuries it’s been in service, every splinter of the Constitution has been replaced at one point or another. Is it still the same ship that traded broadsides with the Guerriere?

That we still think of it as the same ship despite it physically being made up of entirely different material is because of our intuitive sense that there is some essence that defines an object as itself, an essence that is separate from the physical material it’s made of. We see the Constitution as an entity, not merely as a thing made of wood and steel.

Dr. Hood suggests that we have this sense because it helps us identify objects and people as having a continuous existence. He cites a rare neurological disorder in which patients are unable to identify people and objects as those they are familiar with, and instead insist that their parents have been replaced with exact duplicates; and that their closets are full of clothes that are the exact size and style as the ones they own, but belong to other people. Their sense of the essence of objects and people is damaged, and they don’t intuitively connect the beloved parents they spoke with before they became sick with the identical-looking people they’re speaking to right now.

The sense of essence then is extremely useful, as it allows us to intuit continuity. This is even more important with people than with objects. While the entirety of the Constitution has been replaced over the years, it still looks much as it did when it was first launched in the late 1700s. People, on the other hand, change as they age. My daughter today looks almost nothing like she did when she was born. Then she was a tiny, wrinkly, floppy thing that did nothing but eat, sleep, and cry. Now she’s nearly three feet tall, talks incessantly and loves to run and jump. Yet I intuitively see her as the same person.

This brings us to the soul. Our intuitive sense of essence, of a supernatural component to objects’ and peoples’ identity, lends itself to the instinctive assumption that there is metaphysical soul which animates our physical body. The sense of essence creates the illusion that there is something more to the people we interact with than their physical bodies, and together with other phenomena, such as our experience of our consciousness as existing in a metaphysical space somewhere behind our eyes; our sense that we occupy our bodies and drive them around like meaty vehicles; our difficulty truly conceiving of our own non-existence and a world that we are not a part of in some way; and the lack of obvious physical change at the moment of death, causes us to infer a metaphysical entity that animates the body and is the actual person we are interacting with – a soul.

Unfortunately for proponents of the existence of a soul, none of these things are evidence that a soul exists. Intuiting essence is useful to us because it lets us identify objects as having a continuous existence, but essences aren’t real in an objective sense – for either ships or people. Our sense of our consciousness as separate from and in control of our bodies is just a quirk of experience – our consciousness is an emergent property of our brains, and some of the brain areas responsible for various experiences have already been identified. Our consciousness is not any one of the experiences produced by discrete areas of the brain, but the sum of those experiences. Our difficulty conceiving of a world in which we do not exist is due to our complete lack of experience with our own non-existence – an experience that would be impossible to have. And the lack of an obvious change that turns a person into a corpse is because we cannot detect brain activity without sophisticated equipment. People die because their body breaks and stops working, much the same way a computer will stop working if a circuit board is cracked. There is no ghost in the machine that makes a computer work, just silicon chips, ceramic platters, and electric current. And there is no need to posit a soul to animate our bodies, just neurons, neurotransmitters, and bioelectricity.


  1. Very interesting--I'd like to read this book.

    The Just World Hypothesis did something similar for me in regards to belief in moral order in the universe.

  2. Good stuff.

    In case you are interested and have Itunes, there is an Itunes U philosophy course from Yale on Death and afterlife, covers the subject of soul in great detail. I love listening to it on my drive to work

  3. Unfortuneatly, I don't have Itunes. Do you know if its available anywhere as an mp3?

  4. http://oyc.yale.edu/philosophy/death