Christian Jarrett has an interesting article at BBC Future on the number of senses that we have.
The principle of five basic human senses is often traced back to Aristotle’s De Anima (On the Soul), in which he devotes a separate chapter to vision, hearing, touch, smell and taste. Today, the five senses are considered such an elementary truth that it is sometimes used as a point of consensus before writers embark on more mysterious or contentious topics. “What do we actually mean by reality?” asked the author of a recent article in New Scientist magazine. “A straightforward answer is that it means everything that appears to our five senses.”
If only it were that simple. Simply defining what we mean by a “sense” leads you down a slippery slope into philosophy. One, somewhat vague, definition might argue that a human sense is simply a unique way for the brain to receive information about the world and the body. If that is the case, then we can claim with confidence that there are certainly more than five human senses.
Jarrett goes on to discuss a number of additional senses such as proprioception (our sense of where our body and body parts are), our sense of balance, hunger, thirst, as well as the fact that the five “classic” senses could be split into many additional ones.
Of course, you could also be reductive about this:
At the other extreme, you could restrict our definition of discrete sense to the physical categories of incoming information. We can simplify the human senses down to just three – mechanical (which takes in touch, hearing and proprioception); chemical (including taste, smell and internal senses); and light.
You could be even more reductive and insist that there is only one sense, that of touch. This would include what we traditionally mean by touching such as something coming into contact with your arm, but also the touch of photons hitting the receptors in your eyes or the touch of gas molecules to the smell receptors in your nose.
However, a strong case could be made that being so reductive isn’t really productive. All of our senses may reduce to receiving electrical signals caused by matter or energy connecting with our body, but that certainly isn’t the way we perceive things. For purposes of studying the senses, it makes more sense to categorize the ones that we perceive differently, even if that perception ultimately amounts to illusion.
This reminds me of the perennial debates on free will. Once we decide that the mind is simply a logical construct of the physical brain, is there any room for free will? Many insist no. Our thoughts are driven by the laws of physics and therefore we must simply learn to live in that universe.
But most of those who make that insistence are also careful to clarify that they’re not endorsing fatalism. Our decisions ultimately are controlled by physics, but we still have to make those decisions, and it’s not productive to simply not decide, to do nothing and consign our fate to the laws of nature. Indeed, many of them would argue that we have a responsibility to gather the facts and make the best, most informed decisions that we can, particularly on ethical decisions such as whether or not to fight global warming, vaccinations, or faith healing.
The compatibilist position is simply to call the above “free will”, that it remains a useful concept, that insisting that it is an illusion is akin to insisting that the distinct senses are illusions, or that the game of football is an illusion, or the Mac OS X software on my laptop, or even this blog post. None of these things can be physically pointed to. They all only exist as patterns that we’ve given labels to.
A strict reductionist could insist that there is nothing but space, fermions, and bosons, and that all else are merely patterns built on top of these entities. It’s possible that even these elementary particles are patterns of lower level realities. It’s even possible that there is no base reality, that everything is patterns all the way down. Ultimately, it may all be emergent.
We continue to regard things like Mac OS X, a table, a tree, and many other concepts as existing in their own right, because it is productive to do so. And we regard ourselves as having several senses, because it is productive to do so.
But we continue to argue whether it’s productive to regard free will as real. Given that most of us agree that fatalism is not a productive outlook, I often wonder if a term like “volition” was used instead of the theologically loaded “free will”, whether it wouldn’t make this debate moot.
The problem, of course, is that “free will” is a term heavily embedded in law, philosophy, and much of society. The opponents of free will, who are often atheist activists, usually assert that the intuitive version of free will is the theological version involving a separate soul, and that because of this, the term needs to go. However, empirical studies have not backed up those assertions.
Most people, it seems, intuitively regard “free will” as more or less synonymous with volition. Although, to be honest, other studies have shown that most people are also intuitive dualists, and if explicitly asked if these concepts were related, they would say “yes”.
How many senses do we have? Does free will exist? Is there a reality above fermions and bosons? Is there any one true answer?