[T]he fact that a sentient being is in a state of pleasure is always in itself good, and the fact that a sentient being is in a state of pain always in itself bad, when this fact is not an element in a more complex fact having some other characteristic relevant to goodness or badness. And where considerations of desert or of moral good or evil do not enter, i.e. in the case of animals, the fact that a sentient being is feeling pleasure or pain is the whole fact (or the fact sufficiently described to enable us to judge of its goodness or badness), and we need not hesitate to say that the pleasure of animals is always good, and the pain of animals always bad, in itself and apart from its consequences. But when a moral being is feeling a pleasure or pain that is deserved or undeserved, or a pleasure or pain that implies a good or a bad disposition, the total fact is quite inadequately described if we say 'a sentient being is feeling pleasure, or pain'. The total fact may be that 'a sentient and moral being is feeling a pleasure that is undeserved, or that is the realization of a vicious disposition', and though the fact included in this, that 'a sentient being is feeling pleasure' would be good if it stood alone, that creates only a presumption that the total fact is good, and a presumption that is outweighed by the other element in the total fact.
(W. D. Ross, The Right and the Good [Indianapolis: Hackett Publishing Company, 1988], 137 [first published in 1930])
Note from KBJ: Since the concepts of desert and good or bad disposition do not apply to animals (who are not moral agents), their pleasure is intrinsically good and their pain intrinsically bad. (Animals, unlike humans, never deserve to suffer or to be happy, for they are not morally responsible for their behavior.) For beings (such as normal humans) to whom the concepts of desert and good or bad disposition apply, things are more complicated. Pleasure is good when, and only when, it is deserved. Pain is bad when, and only when, it is undeserved. We can say, therefore, that animal pleasure is always good, whereas human pleasure is only sometimes good; and also that animal pain is always bad, whereas human pain is only sometimes bad.