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Philosophy And Mental Illness

“I think therefore I am” – Renee Descartes (1640) It is a beautiful summers day and you are walking in the countryside. In a clearing to your right you see a cherry tree, the red fruit peeping from under the lush green foliage. You walk up to it. You touch it, feeling the rough bark under your fingertips. You can hear the breeze rustling the leaves, and smell the odour of the fruit. You take a cherry and pop it in your mouth, savouring the sweet juice as it floods over your tongue.

But does the cherry tree exist? You can see it, hear it, feel it, smell and taste it’s fruit – but this is not enough. You may be hallucinating, or asleep and having a particularly vivid dream. How would you know? You wouldn’t. All our experience of the world and “reality” is governed by our five senses (I leave aside any discussion of a “sixth sense”). These senses are our only connection with the world outside our selves.

A blind person has no visual contact with the outside world; somebody with a severe cold has little taste or olfactory contact with the outside world. And these senses are basically biochemical machines designed to send information to our brain. For example, the eyes collect and focus reflected light onto the retina (at the back of the eye). Receptors in the retina convert this light into electrical impulses (this electricity is produced by chemicals in the receptors). These electrical impulses are then fired along a network of nerve cells to the brain. The brain, another very complex mass of interconnected nerve cells, analyses these impulses – their strength, their rate, their pattern and frequency – and generates an internal picture based upon them. It is this brain-generated picture that we “see”. It is a similar case with the sensation of touch. Receptors in our skin are stimulated by physical contact and produce electrical impulses that are sent to the brain – what we “feel” is the result of the brain’s analysis of these impulses. And so on for taste, smell and hearing.

So the tree that we saw, felt, heard, smelled and tasted isn’t actually “out there” in the world – it is in our brains. More accurately, it is the brains image or impression of the tree constructed from the impulses it receives from our senses. Whenever our brain received this particular pattern of impulses from the senses, it would construct an image of a tree – colour, shape, smell, taste, touch and sound – whether or not a tree was actually there. There is little controversy in stating that our brains can be deceived. We can block the path of the electrical impulses as they pass from the sense receptors to the brain – this is the case with local anaesthesia, where a patient can watch as his appendix is removed without pain. Or we can interfere directly with the brains analysis of the sense impulses – a drunken person is aware that he has fallen over, but it doesn’t hurt (until the next day!). And we don’t need alcohol or drugs for this deception to occur – at some point, most of us have believed, albeit briefly, that we’ve seen or heard or felt something that has turned out to not be there. It was this sort of reasoning that led Descartes to question the very existence of a world outside our selves. In light of modern science, Descartes is questioning the existence of a world outside our brains (our bodily sensations such as feeling hungry or having an aching leg are also mediated by our senses). In these terms, our own bodies are considered as part of the outside world.

If all we see, hear, touch, feel and taste in the outside world is but a representation in our brains, and this representation is based on information from our senses, and these senses can be deceived, then we can never be sure that the outside world exists. Descartes talked of the possibility of us being hypnotised by a demon who is tricking us into believing we are moving around in a world with trees, houses, other people etc when in fact we’re locked in a dungeon somewhere. The film “The Matrix” provides a technological alternative. So we can’t know if the outside world exists – it could all be in our brains. But in that case can we know that anything exists? Thankfully, yes. We can be sure our thoughts exist. How? Because we think them. There seems no way that we can be deceived about our thoughts existing – in the very act of having a thought, that thought exists. The thoughts may be based on deceptive information from the senses, but they are still real, they still exist. It is difficult to conceive of deceiving someone into believing they have thoughts when, in fact, they don’t.

You need to have thoughts to be deceived. So we can safely say that our thoughts definitely exist! Descartes moved on from this “rock of certainty” and went on to “prove” the existence of the outside world. Unfortunately, this further “proof” is highly suspect and relies on the notion of a beneficent and all-powerful God – but then Descartes was writing on behalf of the Catholic Church! Most modern philosophers discount this extension of his theory, but they do still accept his earlier reasoning - “I think therefore I am” has stood the test of time. If we are being pedantic, Descartes quote is better rendered as “There are thoughts” – just because I experience thoughts doesn’t mean they are mine! But this isn’t as memorable as the original. So what has all this got to do with mental health? Well, if the outside world doesn’t exist as such and all we have is thoughts, then (potentially) the world is what we think it to be. I’m not saying we can change things dramatically. It would take a lot of effort to “create” a thought-world where trees can talk and people fly by flapping their arms – for this to be “real” one would have to interact constantly and consistently with trees and people as though they could do these things. Rather, I am talking about how our thoughts and feelings can “colour” our experience of the outside world (I am using the terms “thoughts” and emotional “feelings” interchangeably here). Depressed people (i.


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