I stood among them, but not of them.

--- Lord Byron, cited by Todd Bucholtz in "New ideas from dead economists", 1989, p 106

More info, from http://www.online-literature.com:

I stood
Among them, but not of them; in a shroud
Of thoughts which were not their thoughts.

Childe Harold’s Pilgrimage, Canto iii. Stanza 113.