From Hobson's Choice
A sentient being is used here as a synonym for "person."
The defining attribute of a sentient being is the ability to sense inwardly; the ability, in particular, to experience satisfaction (the fulfillment of a goal), frustration, and anguish. Sentient beings derive their moral rights from their ability to have conscious desires and form plans for their pursuit.
- John Rawls, A Theory of Justice, Belknap Press (1971)
James R MacLean (23:19, 14 October 2007 (PDT))