Firstly , animals are known to experience emotional distress and even depression . Animals are emotional creatures . To what extent we won ' t ever really know but if we assume that they can ' t suffer we allow ourselves to make a huge mistake . Secondly , and more importantly , I think contemporary ethics is more so based in freewill than the ability to suffer . It ' s bad for you to harm me not only because I would suffer but also because you ' re infringing on my ability to exercise freewill . Freewill is the root of Kant ' s ethics , it ' s the aspect of nature that plays the concrete base for ethics . If we only cared about suffering then there wouldn ' t be anything wrong with shooting you in the head because that wouldn ' t cause you any suffering assuming killing you doesn ' t cause others to suffer . That doesn ' t seem right .