Assigning Rights to Beings
Man has difficulty proving his own existence, so it would
be difficult to "prove" sentience should matter in assigning rights more than,
say, being purple. So in a "proof", sentience is part of a starting assumption.
With assumptions, there needs not be logic. Accept them or not.
Some folks will contend that rights are given
only as part of social contracts, and that until Society chooses to
give rights, nobody has them.
Unfortunately, this position doesn't require Society to be
consistent in any way.
So it is more intellectually consistent to choose a line,
and for most Animal Rights advocates, sentience is only one factor in that
choice. It is not an easily defined line. But then, neither is "being
human"--which spawns the abortion debates.
If someone agrees that sentience is to be given ANY merit,
then animals should be accorded some rights (to be logically consistent).
Tom Regan uses sentience only as a starting point in his
theory, and he makes it clear that sentience is not enough for rights. Rather,
in order for a human or non-human to be regarded as a right holder, the being in
question must not only be sentient, but must be regarded as a "subject of a
life." That is, the being must have a psychological status sufficiently complex
so that we may say that the being has preferences, fears, hopes, mood changes,