In the old days, many people thought that animals couldn’t feel anything and therefore had no self-interest. Many Cartesians seem to have taken this view, although according to John Cottingham, Descartes himself did not defend such a point of view. This type of point of view may have been held by certain behaviorists as well, despite the logical flaw in the passage from “there is no scientific proof that these rats in my laboratory, suffer” to “these rats in my laboratory, do not. not suffer”. In addition, the behaviorist perspective on what constitutes scientific evidence makes it impossible to examine problems concerning suffering.
Others feel that too much emphasis is placed on animal welfare, even though human welfare or basic human rights are still not met for many humans. They cite Africa and many other parts of the world affected by poverty and other problems, sometimes on the rise. These detractors sometimes demand from animal rights activists that before claiming animal rights, they begin by improving the living conditions of their fellow human beings, many of whom live in conditions comparable to, or even worse, those of certain animals.
This criticism assumes the speciesist premise that human suffering deserves greater consideration than any suffering suffered by a non-human animal. Antispeciesists reject this opinion, considering on the contrary that all suffering deserves the same consideration, whatever the species of being who is subjected to it.
More recently, other critics have used Wittgenstein-inspired arguments to defend the idea that certain types of suffering or joy are only accessible to beings who are able to use language. They claim that only humans, bonobos and chimpanzees have this linguistic ability. But logically the fact that humans can feel certain particular sufferings does not mean that one should not seek to eliminate the other types of suffering.
Sometimes opponents of extending animal welfare claim that plants have also feelings, an argument also called the carrot cry.