According to Kant, perfect duties should never be violated; such violations compromise the moral status of the violators. In contrast, imperfect duties can be violated, depending on the situation, without compromising the moral status of the violators.
For example, people have the perfect duty to be honest, which disallows lying, regardless of the situation. In contrast, people have the imperfect duty to be charitable, which allows for situations where people might decide not to be charitable, and those negative decisions fail to imply that the people who make them are immoral.
It relies on a single formula which is relatively easy to understand and apply
It provides a compelling and sensible justification for altruistic action: one should act selflessly when self-sacrifice will produce a greater good for a greater number. As Spock (of Star Trek fame) declares with his dying words, "The needs of the many outweigh the needs of the one!"
It explains and encourages the development of individual moral character. By conscientiously focusing on the needs of the many, and by habitually weighing moral choices with reference to the utility principle, most people would agree that a person develops greater moral sensitivity, greater concern for others, greater strength of will, and thus, a better moral character.
By focusing specifically on consequences rather than blind allegiance to duty or the highly variable dictates of conscience, Utilitarianism answers our intuitions that moral actions ought to produce desirable consequences, if not a better world in general.
Since it does not prioritize any one individual above another, Utilitarianism answers to common modern beliefs that each person is equally valuable and should be given equal weight in making moral decisions.
Utilitarianism is particularly well-suited to address problems of posterity—that is, questions concerning how actions performed today might create problems down the road through have lasting or delayed consequences. Examples of 'problems of posterity' include global warming, pollution, fossil fuel depletion and drilling, endangered species and tropical forest preservation issues, relations between decreased taxation and depleted social security funds, long-term effects of contraception or gender-control birth policies, etc.)
By stipulating that happiness or pleasure must be maximized (and unhappiness or pain minimized) among the "greatest number," without specifying that it must refer only to people, some Utilitarians include animals among the legitimate beneficiaries of our moral choices and see this flexibility as a unique advantage Utilitarianism has over alternate theories. (Some theorists see this same feature as a disadvantage, however, since it further complicates our moral choices.)
Because the utility principle equally valorizes two different variables, it offers no help in deciding which of the two should be prioritized in any given situation—the amount of happiness or the number of those experiencing it.
It denies our moral intuition that duties to family and friends sometimes outweigh our duty to nameless strangers
It ignores appeals to an objective moral ground, upon which legal decisions and ethical claims are most often justified
It implicitly attributes moral fallibility to agents when their actions produce harmful consequences, even if those consequences were unforeseen or unintended.
It often requires impossible foresight regarding the consequences of our actions, and demands that we act in the light of possible consequences even when we can't accurately anticipate or predict them
A criticism specific to Rule-utilitarianism is that when first and second order rules fail us, it simply devolves into Act-utilitarianism
By focusing on the mechanical process of cause and effect, Utilitarianism takes the consistency out of moral action per se, and thus, seems to become (or seems to require that we reduce morality to) an automated process of calculation, with an eye only to results rather than character.
Some critics have argued that by focusing myopically on good ends, utilitarianism tacitly permits or even encourages the use of what many people might consider immoral means to achieving those ends. (The Ends-Means Objection)
Employing a standard like "The greatest good for the greatest number" sometimes requires compromising common beliefs about justice and the value of individuals. Many instances of cover-ups could be rationalized away by claiming that concealing the truth or helping someone avoid prosecution for a crime serves a "greater good."