The Five Senses

Plato's Cave

Plato’s Cave Allegory by Markus Maurer

In the Allegory of the Cave, originally by Socrates, as retold by Plato in his book, The Republic, we are introduced to the idea that we are living in a cave, watching shadows projected on the cave’s wall, from light entering from the outside.  We interpret what these dancing shadows mean but the actual activity that is happening outside is not seen by us just the shadows it projects.  Their point is that we are not watching the real action, just those things our senses allow us to perceive, and thus should not rely entirely on what we think is happening outside.  We need to take everything with a grain of salt, a bit of skepticism, before accepting what our senses tell us.  We may miss or misinterpret what is actually going on around us by just relying on our senses.

Our senses are the data gathering organs we have to interpret our environment and our confidence in those data points is only as reliable as those sensory tools we have.  If we cannot hear very well, a conversation will take on an entirely different meaning if half of it is not heard. The most gourmet meal will lose the subtle nuances and savory tastes if you have a cold and cannot smell.  If you have diabetes you will not feel the pebble in your shoe that will injure the sole of your foot, and which may in the long run cause gangrene and eventually require the amputation of your foot.  Very few blind people go to the movies because it’s too expensive to sit there and just listen to the dialog without seeing the action on the silver screen.  If you are blind you have not been able to drive a car, until just recently, as self-driving cars are becoming more prevalent.

We actually have many more senses than the advertised five that tell us what surrounds us or is within us.  Stretch receptors in the rectum warn us that it is time to find a bathroom.  That sense is so specific that it even gives us the information, and exactly what urgency is required to find that bathroom, or will a nearby bush have to do.   The sense that we need to get some calories in us soon, or that we need to find water to relieve the dryness in our mouth, is not listed in those five senses of smell, taste, sight, hearing, and touch.  Yet without it we would starve or dehydrate to death.  A very important sense we all must pay attention to is the sense of pain.  It tells us not to touch the hot oven plate.  It gives us the clue that we must go to the ER and have the bursting appendix removed before pus spreads through the abdomen and the little tiny invisible plants, called bacteria, seed into our bloodstream, and start feeding on our body.  That cannot last too long before all our vital functions cease, and we become history.

The sense that you have seen that face before, or remember having to turn right at the next corner to get to grandma’s house, gives us our bearings of where we are, and who we should say good morning to in passing.

Many animals have much better tools to detect the environment than we can.  Most dogs can detect one molecule in a trillion molecules, which is about a million times better than we can.  That is why you see dogs at the airport led around by uniformed TSA agents.  They can smell the bomb that is about to blow up the plane you are planning to board. Snakes can detect infrared radiation, and they can use that organ located beween their eyes (the pit) to calculate the exact amount of toxin it will take to kill the prey; hence they are known as pit vipers. An eagle can see a mouse from a thousand feet up in the air.  The octopus eye has a set of internal mirrors that multiplies light, and as a consequence they can see in almost complete darkness. Salmon can locate the exact stream where they were spawned, so they swim back thousands of miles to lay their eggs in the same stream, when they return from their migration to the ocean.  This is the same sense that swallows, Monarch butterflies, and ducks use to navigate transcontinentaly on their yearly migrations.  They sense the earth’s magnetic field lines and are able to interpret and utilize that information to find their way across oceans and continents.  Bees are able to polarize light, which helps them navigate when the sky is cloudy.

We discount that plants have any awareness of their environment, but plants have the ability to respond to environmental conditions to which we are totally oblivious.  They can detect magnetic fields, and particular chemical substances which are either nutrients or noxious to them.   Of course, just as we can, they can respond to light, pressure, water content, and gravitational forces.

Furthermore, there are spectacular events that take place around and within us that we do not recognize at all.  We travel at a tremendous speed all the time, and we think we are standing still.  At the equator the earth rotates at a speed of 25,000 miles every 24 hours.  That is 1041 miles per hour or 150 feet per second, and we are oblivious to it.  That is just rotational travel.  We also travel 584,020,178 miles linearly around the sun in a year (76,000 miles per hour). Yet we do not sense that.  Our bodies are pieced by billions of a variety of sub-atomic particles every second which we do not feel.   Unfortunately, occasionally a gene gets damaged by some of those particles, and that is why 40% of us will get cancer some time in our lives.

Getting back to Socrates, we can’t have all the information because our senses erect walls around us, and give us only partial or misleading information.  Only some of the information gets through the openings in the cave that reaches us, like dancing shadows on the wall of our cave.  It is true that we have extended our senses and have made larger openings in our cave.  We can extend our eyes now and look at molecules with very powerful electron microscopes.  We can even get down to particles within atoms by smashing them with Hadron colliders.  The largest is in Cern, Switzerland.  It is a circular underground tunnel of 17 miles which smashes atoms together and looks for what is left.  We have a variety of tools to measure all the particles that hurl to us from the furthest reaches of space, and we can look further into space than ever before with the most powerful telescopes, one of which, the Hubble telescope is located in space.  Nevertheless, we are still woefully ignorant of why and how things work.

We must be vigilant and question everything before we accept something as truth.  We need to know more than we learned in first grade and even in graduate school.  Don’t believe everything you read or hear, especially what you learned at your grandfather’s knee, in your PhD dissertation, or from your rabbi, priest, or imam.  Be especially vigilant of dogma or dictum that you cannot verify yourself, and question everything, even yourself.