3471. This is the reason why many scholars do not believe in the life after death, nor in the spirit: because they abstract thinking from its organic counterpart, just as they would like to abstract vision and hearing from their organs. I was prompted to add that if thought alone were spirit, what need would one have for such a large brain, since the whole brain is the organ of the inner senses? In that case the skull could be emptied of its contents, and thought would still act the part of spirit - when yet this all could show to the learned of the world that the organics of thought are in the brain, whence there flow invisible fibers, along which thoughts pass from the senses into the organics, and from the organics into the actions of the muscles.
3471. The cause is hence manifest why the learned do not believe in a life after death, nor in spirit, viz., that they abstract thought from its organic [relations], just as they would sight and hearing from their organs. To this we may add, that if spirit was nothing but thought, man would have no need of so much brain as he has, for the whole brain is an organ of the internal senses. Indeed the skull might in that case be wholly emptied of its contents, and still the thought act as spirit. How then can it fail to appear to the learned of the world, that there are organics of thought in the brain, from whence flow invisible fibers, along which the thoughts pass from the [outward] senses to the [interior] organics, and from the organics to the muscular activities?
3471. nifeste [se] percipere [dixit] quod sit organicus; exinde causa apud doctos, quod non credant vitam post mortem, nec spiritum, quia cogitationem abstrahunt ab organico suo, sicut vellent visum et auditum a suis organis: datum addere, si cogitatio solum esset spiritus, quid opus esset homini tanto cerebro, cum totum cerebrum sit organicum sensuum internorum, tunc potuisset cranium esse excavatum, et cogitatio usque agere spiritum; cum tamen exinde constare possit eruditis mundi, quod organica cogitationis sint in cerebro, et inde fluant invisibiles fibrae, per quas cogitationes perducuntur, a sensibus in organica, et ab organicis in musculorum actus.