127-9 humans also have moral duties. Raphael claims that humans and animals both have moral rights. Humans also have moral duties because of their ability to reason and speak. Animals have rights but not duties. It could then be argued that babies and mentally deficient people have rights but not duties.
Children acquire duties only when they attain the reason to understand duty.
However, Raphael does not explain why animals have rights alongside humans. It could be argued that moral right and duty go together and we cannot have one without the other. If I have a moral right to certain behaviour from you, then you have a duty to behave towards me in accordance with my right. Similarly your possession of the same moral right means you can expect the same duty from me. If animals possess moral rights then surely duty of some sort must go with those rights.