Full Idea
If any man could be found so frantic as to deny that he thinks, while he is conscious of it, I may wonder, I may laugh, or I may pity him, but I cannot reason the matter with him.
Gist of Idea
If someone denies that he is thinking when he is conscious of it, we can only laugh
Source
Thomas Reid (Essays on Intellectual Powers 6: Judgement [1785], 5)
Book Reference
Reid,Thomas: 'Inquiry and Essays', ed/tr. Beanblossom /K.Lehrer [Hackett 1983], p.267
A Reaction
An example of the influence of Descartes' Cogito running through all subsequent European philosophy. There remain the usual questions about personal identity which then arise, but Reid addresses those.