The intellectual godfather of this movement is (author of The Case for Animal Rights ). Regan argued that if humans have inherent value simply due to the "subject-of-a-life" criterion (having beliefs, desires, memory, a sense of the future), then so do many adult mammals. Consequently, using them in research or for food is morally indefensible, regardless of how "humanely" it is done.

Governed by the Animal Welfare Act 2006 and the Animal Welfare (Sentience) Act 2022. Features strict enforcement and high welfare standards.

Governed by the "3Rs" framework — Replacement (using non-animal alternatives where possible), Reduction (using fewer animals), and Refinement (modifying procedures to minimize pain).

The concept of animal welfare is grounded in the "Five Freedoms," a set of standards developed in the 1960s to ensure animals do not suffer unnecessarily. These include freedom from hunger and thirst, discomfort, pain or disease, fear and distress, and the freedom to express normal behavior. In modern practice, welfare science uses physiological and behavioral markers to measure stress and happiness. This approach does not necessarily prohibit the use of animals for food, research, or companionship, but it mandates that such use must be governed by strict regulations to minimize suffering.