The conventional argument opposing animal rights is that animals can’t reason like humans, so the notion of “rights” can’t apply to them. Yet not possessing human-like reasoning or intelligence is not a plausible justification for denying someone’s basic interest in not being used as human property.
On the most basic level, all animals have an interest in staying alive, avoiding pain and suffering and experiencing pleasure, raising families and developing complex social structures. (1) For that reason, animals should have at least one basic right: the right not to be used as a resource by another. (2) (Francione, 2010) Forced to become someone else’s resource means denying them expression of their most basic interests. Conventional beliefs about animals simply deny the existence of interests in animals and therefore argue that there are no interests to protect.
Since roughly 99% of animal use is attributable to animals used as food commodities (that we do not require for health or survival (3), we could easily eliminate 99% of our animal use just by not consuming animal products. Whether we love animals or not, the issue of defending their interests with this basic right is not about our love or disdain for one animal or another. It is instead a matter of applying our principle of justice to all sentient animals who clearly and regularly demonstrate an obvious interest in maintaining their own sovereignty.
(1) Beyond these basic interests, animals also possess a range of complex interests on the level of the individual animal as well as on a species level. There are a number of empirical studies and non empirical ways of demonstrating these interests.
(2) Gary Francione, An Introduction to Animal Rights: Your Child or Your Dog