Animal Equality?

While I liked some of Tom Regan's argument for animal rights, there was at least one point which I did not quite agree with.  This was his claim that all animal lives (including those of humans) have equal value, because that value is inherent to the animals being subjects of a life.  Unfortunately, he makes no distinguishment between the values of different sentience levels.  Thus, his view seems as if it could very nearly extend not only to non-human animal lives, but to plant lives and the lives of other non-sentient beings - which is taking it all rather too far for me to agree with.  Saying that life has value simply because it is life does not, to me, seem true.  I would propose that the value of, say, a rabbit's life is higher than the value of a tree's life but less than that of a human's life.  My reasoning is as follows:

Few, I think, would argue that killing a blade of grass is a morally reprehensible act.  This is because the grass cannot suffer, and it cannot enjoy the experience of living or dislike the idea of death.  If the grass blade's life has any inherent value, simply because it is life, then that value is so insignificant as to not even be worth the effort it takes to avoid stepping upon the blade.

As soon as sentience (defined here as awareness; not self-awareness, but any sort of awareness) enters the picture, the value of life shoots up drastically.  Taking the life of a mouse is much harder to justify than taking the life of a blade of grass, because the mouse can suffer - both physically and psychologically - and by killing it one is taking away something that the mouse enjoyed, that is to say the experience of being alive.  Perhaps enjoyed is not quite the right word; valued might be better, in that the mouse preferred being alive to not being alive (although it certainly could not think this through in the same language-based way that most humans can).  If we can agree that sentience gives life value (as I think it does) then all that is left is to determine how we can distinguish which lives are more valuable than others, and how valuable exactly those lives are.

So - if one has a choice between killing and eating a cat, and being hungry for a few hours until one is able to obtain a (vegetarian or vegan) meal, then the cat's life is more valuable than one's appetite or lack thereof, because the cat will suffer upon being killed and will miss out on any life it might have experienced in the future - if one has to wait to eat until the next meal, one will only experience minimal suffering, and no lack of potential future.  If, however, one is starving to death and will die if one does not eat the cat, then one can go ahead and eat the cat, because due to the cat's lower level of intelligence it will suffer at least less psychological trauma by dying, and because its lifespan is shorter than one's own and thus it has less life left to enjoy than one does.

But one could, arguably, also use the principle of self-defense to justify killing and eating the cat, so let us use another example which removes the personal aspect of the situation.  One is starving to death, and has the choice of eating a cat or a similarly sized spider monkey.  In this situation, one would be more morally correct to eat the cat, because it has less intelligence and less life expectancy than the spider monkey.

Some might object to this theory because it seems to place value on life based solely off of life expectancy and intelligence level, and one could argue that humans give more value to the lives of some beings (such as humans with severe mental retardation) than to the lives of others based only off of the fact that those others are not human.  I would disagree.  If a human being's mental powers are, due to some sort of genetic deficiency, on a par with those of a sturgeon, the sturgeon's life has just as much value as that of the human; this is because of the equal intelligence and lifespan (a sturgeon can live at least as long as a human being).  If the human being is eighty years old and the sturgeon is fifteen, then the sturgeon's life has more value, because it has more potential future to enjoy.

This is not to say that we should hunt and devour mentally retarded human beings in the same manner that we do sturgeon!  Instead, it is to say that we should not hunt and devour either of them.  Furthermore, this does not support the (probably extremely unpopular) view that the lives of children have less value than those of adults, or that they have the same value as those of only mentally retarded adults; children will (if mostly psychologically normal) spend most of their future lives at an adult mental level.  Their lesser mental capacity is only temporary, unlike that of a non-human animal or a mentally deficient human.  I would use this argument to contest that vegetarianism or veganism is indeed more morally correct than meat-eating - but not to contest that all non-human animal lives have the same value as one another, or as (average) human lives.  I think that it is morally better to kill a lobster than to kill a goat.

P.S. I am very sorry for the horrendous length of this post - alas, I could not see how to shorten it or divide it up into smaller posts without losing the coherency of my point.