Full Idea
'Sentience' comes in every imaginable grade or intensity, from the simplest and most 'robotic', to the most exquisitely sensitive, hyper-reactive 'human'. We have to draw a line for moral policy, but it is unlikely we will ever discover a threshold.
Gist of Idea
Sentience comes in grades from robotic to super-human; we only draw a line for moral reasons
Source
Daniel C. Dennett (Kinds of Minds [1996], Ch.4)
Book Reference
Dennett,Daniel C.: 'Kinds of Minds' [Phoenix 1997], p.128
A Reaction
This is the only plausible view, if you take the theory of evolution seriously. We can even observe low-grade marginal sentience in our own minds, and then shoot up the scale when we focus our minds properly on an object.