Appendix - 6. (451).
The second of the four demonstrations of the simplicity of the sentient principle given in Anthropology is based on the fact of the duplication of organs in certain sensories such as the eyes and ears, etc. and their corresponding simple sensations. The force of this proof, therefore, depends on showing that there are two sensory organs, and consequently two sensations received by the soul which then makes them one through its own simplicity. Roland's experiment shows that the optic nerves are not united in the brain, as some people suspected, but that there are two clearly distinct sight organs, not one. The proof becomes even more effective if we consider that the optic nerve of the right eye terminates in the left lobe and that of the left eye in the right lobe. Granted the twofold nature of these sensations, it is not surprising that Doctor Gall made every effort to prove that we always see with one eye alone. There is no doubt that the fact of our seeing simultaneously with both eyes must have been a severe embarrassment to a system as materialistic as his. Nevertheless, says Magendie,
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it has been shown, that the two eyes not only concur in vision, but that it is altogether necessary that both operate if certain acts, extremely important to sight, are to be carried out. - Let a ray of sun fall on a plate in a darkened room. Then take two pieces of very thick glass, each coloured with colours of the prism, and put them to the eyes. If your sight is good, and especially if the eyes are of equal strength, the image of the sun will appear whitish, whatever colour glass you use. But if one of your eyes is much stronger than the other, you will see the image of the sun coloured according to the colour of the glass you have put to the stronger eye. These results were verified in the presence of Mr. Tillaye junior in the physics laboratory of the faculty of medicine. A single object, therefore, really produces two impressions. The brain nevertheless perceives only one of them (Précis élémentaire de Physiologie, Action simultanée des deux yeux). |
The consequence Magendie draws from the fact he has noted is absurd. He concludes that the brain perceives only one of the two impressions. This is a clear proof of the incredible force possessed by educational prejudice in distracting the most perspicacious minds, despite every effort to avoid unproved assertions. The learned physiologist acknowledges that each eye receives not only a single, distinct impression, but an impression accompanied by sensation. He knows through his own anatomical experiments that each of the nerves terminates in a different lobe of the brain; nevertheless he asserts with the highest surety that the brain has only a single impression because of the presence of a single sensation! Anyone with a little common sense is capable of recognising here that the brain can neither simplify the two distinct impressions which it undoubtedly receives nor fuse the two sensations (which do not arise in the extrasubjective brain) into a single sensation; it can fuse them only in the subjective feeling, that is, in the soul. The simplicity of the soul is alone capable of explaining how two sensations, when having wholly equal positions in what is felt fundamentally, necessarily change into one because the space which divides them and makes them appear two is lacking. My own experiment, made without glasses, consists in fixing the eyes on a piece of paper painted with two columns of different colours. Cross the eyes so that one colour is superimposed on the other. The result is that one colour is changed by the other in the same way as different colours of transparent glass when imposed on one another. This is another proof of the simplicity of the soul (cf. AMS, 107).
Magendie himself has this to say about the twofold sensation given by the two ears:
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It has been said incorrectly that we use one ear at a time. When dealing with the direction of sound and deciding where it originates, we are obliged to employ both ears. Only by comparing the intensity of the two impressions can we recognise the source of the sound. If, for example, we completely block one ear when a slight sound is being made some distance away in a dark place, it will be impossible to judge the direction of the sound which can, however, be recognised if we make use of both ears (Précis élémentaire de Physiologie, Action simultanée des deux appareils de l'ouïe). |
How can he say, therefore, that the brain receives only one sensation?
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