It has been pointed out to me before that thoughts and dreams are an amazing thing because everything you see and hear is coming out from nowhere. The fact that you can see and hear without your eyes and ears, it is said, is absolutely astounding. How can there be sound without physical sound, vision without physical vision? This is often used as an argument for the existence of a soul, the soul being a convenient vessel for it (as it is an oh so conveniently immaterial thing). It’s not a good argument and here is the main reason why: the only difference between hearing your own thoughts and hearing someone else’s voice is input. We tend to forget that what we sense is then completely re-assembled by our brain. Any educated person knows that the the reality that seems to appear in front of our eyes is actually the image inside our brain. The continous stream of the outside world we’re experiencing right now is not the outside world per se, but the image of the outside world your brain has concocted. When you mull that fact over, you can get a bit of an eery feeling, even though you implicitely know this to be true. Colors are meaningless without eyes and a brain. You cannot claim something is red if you don’t include human eyes in the equation (we implicitely do of course so we do say that some things are red and that makes sense to everyone). The brain is capable to build colors, depth, sounds and feelings of warmth and pain. Forgetting that all this hardware is in the brain and putting it outside into the world is what makes people come up with the faulty argument that there’s something somehow much more special about hearing a voice in your head even though there is no sound to make it. Light is produced by photons hitting your retina and sound is produced by the displacement of air. but those are not truly the image you see and the sound you hear until your brain makes sense of them. So if our brain has all this wonderful hardware to create all these wonderful sensations from some fairly simple input, why would it be so hard to conceive of immaterial thought (and images when dreaming) arising from the same process? Instead of the brain being triggered by signals from the eyes and the ears, it is triggered by itself. Once you’ve accepted that all the stuff you need to form sensations with is already in the brain, adding a self-trigger seems fairly conspicuous. So hearing voices without any input is no more impressive than hearing voices with. It’s the same basic phenomenon with a different source triggering it.
While I was writing this first paragraph, a question came to my mind. Could animals be experiencing a completely different array of sensations to us? By that I do not mean seeing different colors or hearing a different set of sounds, this we already know to be the case to a certain degree of certitude. We all have common ancestors with different species down the line, so it’s no big leap of the imagination to deduce that the mind of a cat, whose ancestor with us developed a brain and eyes that went on to diverge somewhat, shares much of the perceptual hardware we have. What I mean is sensations we can’t even imagine because we don’t have a referential for them. Just as earlier I argued that color makes no sense without considering an eye and the brain that goes with it, could there be something in the mind of an animal that cannot be conceived without this hardware, that would be alien to us as we do not posess a reference point for it? This reminds me of the idea that is often proposed that bats perceive something like vision when they use echolocation. That makes some sense. It could also be something radically unlike vision, there’s no way of knowing, unless you experience being a bat. It’s an interesting thought to ponder.