An intrinsic good is something which is valuable in and of itself, such as pleasure. If there are intrinsic goods, then we clearly have a duty to bring them out. Some duties are based specifically on the intrinsic goodness of pleasure, as experienced by others and ourselves. Justice also is founded on the intrinsic goodness of pleasure. Other duties are derivatives of these four.
Reparation involves a duty arising from harm which has been done.
Gratitude arises from the beneficence which has been shown to us by others. He also notes that there are compound duties which arise from the above seven. Political obedience, for example, arises from gratitude for benefits we receive from the state. Ross recognizes that the manner in which our actual duty emerges from prima facie duties is difficult to articulate. It is similar to the laws of mechanics, he argues, insofar as several forces add together to produce a given tendency.