With approximately 65 billion animals killed annually for food, farm animals are the most numerous animals subjected to cruelty.
Divergent approaches to laws concerning animal cruelty occur in different jurisdictions throughout the world.
It has been suggested the number of animals hunted, kept as companions, used in laboratories, reared for the fur industry, raced, and used in zoos and circuses, is insignificant compared to farm animals, and therefore the "animal welfare issue" is numerically reducible to the "farm animal welfare issue".
Similarly, it has been suggested by campaign groups that chickens, cows, pigs, and other farm animals are among the most numerous animals subjected to cruelty.
Others argue that psychiatry and other authorities outside of courts keep records of who have been cruel to animals and can make biased guesses about whether or not they did violence to humans thereafter and also that they conversely record people who have been violent to humans and can be more biased towards later assuming them to have been cruel to animals, explaining apparent links by institutional bias without link between the actions themselves.
Another criticism of these studies is the definition of cruelty as "socially disapproved behavior".
They say that the only way to ensure protection for animals is to end their status as property and to ensure that they are never used as a substance or as a non-living thing.
Throughout history, humans believed in a God-given right to treat nonhuman animals with cruelty; however, some individuals, like Leonardo da Vinci for example, who once purchased caged birds in order to set them free, In Cartesian dualism, consciousness was unique to human among all other animals and linked to physical matter by divine grace.
Passive cruelty is typified by cases of neglect, in which the cruelty is a lack of action rather than the action itself.
Oftentimes passive animal cruelty is accidental, born of ignorance.