The moral circle — the boundary of beings we consider to have morally relevant interests — has expanded historically. Understanding this trajectory helps welfare advocates position their work in historical context.
The expansion of moral concern to animals represents one of the most significant ethical shifts in Western history. The recognition that non-human animals have interests that deserve consideration — that causing unnecessary suffering to animals is wrong regardless of human benefit — is a relatively recent development that continues to evolve. The trajectory from limited protection for large vertebrates to recognition of decapod crustacean sentience in UK law reflects both advancing scientific understanding and shifting moral philosophy. Welfare advocates stand in a long tradition of expanding who counts morally, and can draw confidence from this historical trajectory.