Utilitarianism is ultimately the child of egoism and Kantian Duty. It can be defined as what an individual views as being best for them and the people surrounded by them who are affected by their actions. It is then broken down into two units, act utilitarianism and rule utilitarianism. Evaluating actions and selecting one over the over based on which one produces the greatest amount of happiness is act utilitarianism. So on, rule utilitarianism is determining the morality of an action based on the value of its consequence if the rule was to be followed. Stephan Darwall analyzes Mill's theory of both and gives his objections and contradictions that shines a different light on the outcome of the theories.
"A criterion of what makes an action the right thing to do" is how Darwall decides to define act utilitarianism. Before critiquing the theory he lays out all the components that play a role in it. He begins by pointing out that act utilitarianism is a quantitative principle that emphasizes on the measurement of happiness. Continuing his analysis he describes the occurrences of "wherever, whenever, and whomever" that arise when calculating the value of an actions pleasure. In his "wherever" description the result of happiness/unhappiness the action would cause in means of how close or far away it occurred is key. "Whenever" indicates how the action would be effective time wise whether it's present or future tense. Evidently, "whomever" explains the people who would be affected by the action including one's self. He touches on how in the definition of act utilitarianism "net" should be paid attention too. Significantly that net happiness is the sum of an actions unhappiness minus its happiness. Concluding his analysis of the important components of act utilitarianism he puts emphasis on the word "greatest" ultimately stating that it isn't just enough for an actions aftereffect to be good but it must result in the best outcome of all choices presented.