The second feature of perception that the passage quoted above refers to is the distinction Reid draws between original perception and acquired perception : in the case of original perception, a natural sign (that is, a sensation) suggests a conception and a belief “by original principles of our constitution.” In the case of acquired perception, by contrast, the natural sign in question suggests a conception and a belief “by custom,” which most probably means “habit” and/or “experience.” Let us take a closer look at this distinction by pinning down some of the essential features of original perception, and by emphasizing some of the points of departures from this model, in the case of acquired perception.
Instead of printing transcriptions of a selection of manuscripts, we have created a guide to the manuscripts in the notes to the text, so that the interested reader can follow up on points of particular interest. The Reid manuscripts are of such extent and complication that such an exercise has to be selective and consequently done from the point of view of the editors, but this would obviously be even more the case with the printing of manuscripts, however generous. This decision should not be seen as belittling the importance of the manuscripts; to the contrary, we are elated that the reader is now able to make much more comprehensive use of this material than we could ever hope to achieve by reproduction of material and to do so guided by his or her own interests. The basic editorial principle has been to leave Reid’s intentions as clear as possible for the reader to interpret, and this can often be done by encouraging the pursuit of manuscripts that identify matters only alluded to in the final text and that indicate the development of arguments.