Hartley's theory of the human mind : on the principle of the association of ideas; with essays relating to the subject of it / By Joseph Priestley.

  • Hartley, David, 1705-1757.
Date:
1775
Catalogue details

Licence: Public Domain Mark

Credit: Hartley's theory of the human mind : on the principle of the association of ideas; with essays relating to the subject of it / By Joseph Priestley. Source: Wellcome Collection.

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    * There will be no great difficulty in conceiving that, in a fubftance not fluid, like the air, but [olid, though foft, like the brain, a vibration affe&ing any part of it will leave that part difpofed to vibrate in that particular manner rather than in any other; fo that a fecond impreflion of the fame kind may be diftinguifhed from a fiyfl; which may, in force me aha re, explain the difference between a new fenfation, and the repetition of an old one. But thefe are chiefly diftinguifhable from one another by the difference of their aflfociations, both with other ideas, and with a different date of the mind, or brain, in a variety of refpeds. Alfo, one vibration having been diffidently im- preffed, it may be conceived that the region of the brain affe&ed by it will retain a difpofition to the fame vibrations in preference to others: fo that thefe vibrations may take place from other caufes than the original one. But thefe vibrations will neceffarily differ confiderably in ftrength, and other eircumftances, from original vibrations; which provides for the difference between the ideas of prefent obje&s, and the fame idea excited with¬ out the prefence of the objedt. Thus circles of colours may be excited by prefling the eye with the finger, and by other caufes, which, however, are eafily diftinguifhed from a fimilar affe&ion of the retina by the impreflion of rays of light. If it be faid that thefe vibrations in the brain, differing chiefly in degree, might be liable to be miftaken