Full Idea
If it be made a question whether the toothache be in the mind that feels it, or in tooth that is affected, much might be said on both sides, while it is not observed that the word has two meanings.
Gist of Idea
It is unclear whether a toothache is in the mind or in the tooth, but the word has a single meaning
Source
Thomas Reid (Essays on Intellectual Powers 2: Senses [1785], 18)
Book Reference
Reid,Thomas: 'Inquiry and Essays', ed/tr. Beanblossom /K.Lehrer [Hackett 1983], p.187
A Reaction
I'm glad Reid was struck by the weird phenomenon of the brain apparently 'projecting' a pain into a tooth. Presumably before the brain's role was known, people were unaware of this puzzle. There certainly are not two distinct experiences.