| "> | | | | âsixth senseâ). These senses are |
| âI think therefore I amâ â | | | | our only connection with the world outside our selves. |
| Renee Descartes (1640) | | | | A blind person has no visual contact with the outside |
| It is a beautiful summers day and you are walking in | | | | world; somebody with a severe cold has little taste |
| the countryside. In a clearing to your right you see a | | | | or olfactory contact with the outside world. And |
| cherry tree, the red fruit peeping from under the lush | | | | these senses are basically biochemical machines |
| green foliage. You walk up to it. You touch it, feeling | | | | designed to send information to our brain. For |
| the rough bark under your fingertips. You can hear | | | | example, the eyes collect and focus reflected light |
| the breeze rustling the leaves, and smell the odour of | | | | onto the retina (at the back of the eye). Receptors |
| the fruit. You take a cherry and pop it in your mouth, | | | | in the retina convert this light into electrical impulses |
| savouring the sweet juice as it floods over your | | | | (this electricity is produced by chemicals in the |
| tongue. | | | | receptors). These electrical impulses are then fired |
| But does the cherry tree exist? You can see it, hear | | | | along a network of nerve cells to the brain. The |
| it, feel it, smell and taste itâs fruit â | | | | brain, another very complex mass of interconnected |
| but this is not enough. You may be hallucinating, or | | | | nerve cells, analyses these impulses â their |
| asleep and having a particularly vivid dream. How | | | | strength, their rate, their pattern and frequency |
| would you know? | | | | â and generates an internal picture based |
| You wouldnât. All our experience of the | | | | upon them. It is this brain-generated picture that we |
| world and ârealityâ is governed by | | | | âseeâ. It is a similar case with the |
| our five senses (I leave aside any discussion of a | | | | sensation of touch. |