What arguments did Peter Singer make against factory farming?

In his influential 1975 work, Animal Liberation, Peter Singer argued against factory farming by highlighting the routine suffering and abuse of animals within the industry. His critique is grounded in utilitarianism, which posits that actions are morally right or wrong based on their impact on happiness or pain.1

Singer’s core arguments include:

• Rejection of Speciesism: Singer argues that species membership is not a morally relevant characteristic. He contends that all beings capable of suffering or enjoyment have interests that must be considered equally, regardless of their species.12
• Principle of Equal Consideration (PEC): He asserts that we must give equal weight to the like interests of all beings. Because animals are capable of feeling pain, they have a fundamental interest in avoiding it, which deserves the same moral consideration as a human's interest in avoiding pain.2
• Moral Consistency: Singer maintains that favoring human interests over animal interests simply because of species is a form of prejudice analogous to racism or sexism.12

By applying these ethical principles, Singer concludes that the systemic pain inflicted by factory farming is morally indefensible.12