Thomas Beddoes to Erasmus Darwin, [July/August 1794]
Dear Sir,
I cannot help supposing ‘ideas’ to be motions of the fibres of the organs of sense; your evidence is as satisfactory as indirect evidence can be, and at least equals in strength that which Harvey adduced in support of the circulation. Therefore of late the term ‘idea’ has always been synonimous with me to a system of moving filaments fibrarum micantium; hence I distinguish objects from ideas only in so far as the latter have never actually been perceived; it may therefore be superfluous to say that objects are known to be the same from the sameness of the perceptions they excite; but of the nature of sensual motions we have no perception; and therefore cannot tell whether ideas are imitations of the objects that excite them: it appears to me as if you did not distinguish between the passive and the active circumstances, when the sense of touch, for instance, is stimulated. By the active and the passive I mean the second and first parts of a perception, as stated by you at (p. 111, top.) So also the passive and active circumstances in vision are distinguishable. I perceive the figure at the bottom of the eye to resemble the shadow projected from the tree; but of the manner of contraction of the retina I have no direct or indirect sensible knowledge; i.e. I am utterly ignorant: from the fibrous structure I should conjecture the effect of the stimulus extended beyond the portion of the organ of sense to which it is applied; thus suppose a plane surface of any size touching the shin; fibres running beyond the touched part will probably contract through their whole length. You may say the sensual differ from the muscular fibres in their organization so as only to contract where stimulated; but is not this a mere supposition?
Your’s with much esteem,
Thomas Beddoes
Published: Stock, Appendix 6, p. xliv