: The first major animal protection law was Britain’s Cruel Treatment of Cattle Act (1822), followed by the formation of the Royal Society for the Prevention of Cruelty to Animals (RSPCA) in 1824. These early laws targeted overt cruelty—bear-baiting, overworking draft horses, brutal slaughter methods. The American SPCA followed in 1866. This was pure welfarism: reducing visible suffering without challenging the economic or social order.

: Where sentient beings exist, causing them unnecessary harm requires justification. The debate is over what counts as “necessary.”

: All 50 U.S. states have felony animal cruelty laws, but they are inconsistently enforced. Moreover, “standard agricultural practices” are almost universally exempt. A person can be prosecuted for leaving a dog in a hot car, but a pig can be legally confined in a gestation crate so small she cannot turn around for most of her pregnancy. The law carves out animals based on their use : companion animals get protection; agricultural animals get exemptions.

: The publication of Peter Singer’s Animal Liberation (1975) changed everything. Singer, a utilitarian philosopher, argued that the principle of equal consideration of interests applied across species. If a pig suffers as much as a human child, their suffering deserves equal moral weight. While Singer himself is a welfarist (he supports gradual reform), his work gave birth to the modern animal rights movement. Tom Regan’s The Case for Animal Rights (1983) provided the deontological argument: animals have inherent value, period.