As we mentioned, Kant restricts having intrinsic value or being an end in
itself to rational beings, but it is difficult to see why this should be so. Surely
any sentient or conscious being has states that matter to it in a positive or
negative way—pleasure matters to an animal in a positive way, pain or fear
in a negative way. Since it can value what happens to it, it has intrinsic
value. Given the logic of morality, we should extend our moral attention
to those states that matter to it when our actions affect that being. So what
if it can’t reason?—not all or even most of our moral attention focuses on
reason vis a vis people. Most of it in fact focuses on feeling, on not hurting
people physically or mentally, or helping them be happy or escape from
suffering. So if human beings are ends in themselves, why not animals,
since they too have feelings and goals that they value?
(Bernard E. Rollin, "Reasonable Partiality and Animal Ethics," Ethical Theory and Moral Practice 8 [April 2005]: 105-21, at 117)