1. Trolley:
There is a runaway trolley barreling down the railway tracks. Ahead, on the tracks, there are five people tied up and unable to move. The trolley is headed straight for them. You are standing some distance off in the train yard, next to a lever. If you pull this lever, the trolley will switch to a different set of tracks. However, you notice that there is one person on the side track. You do not have the ability to operate the lever in a way that would cause the trolley to derail without loss of life (for example, holding the lever in an intermediate position so that the trolley goes between the two sets of tracks, or pulling the lever after the front wheels pass the switch, but before the rear wheels do). You have two options: (1) Do nothing, and the trolley kills the five people on the main track. (2) Pull the lever, diverting the trolley onto the side track where it will kill one person. Which is the correct choice?

2. Fat man:
As before, a trolley is hurtling down a track towards five people. You are on a bridge under which it will pass, and you can stop it by dropping a heavy weight in front of it. As it happens, there is a very fat man next to you – your only way to stop the trolley is to push him over the bridge and onto the track, killing him to save five. Should you proceed?

3. Transplant:
A brilliant transplant surgeon has five patients, each in need of a different organ, each of whom will die without that organ. Unfortunately, there are no organs available to perform any of these five transplant operations. A healthy young traveler, just passing through the city the doctor works in, comes in for a routine checkup. In the course of doing the checkup, the doctor discovers that his organs are compatible with all five of his dying patients. Suppose further that if the young man were to disappear, no one would suspect the doctor.

4. Utilitarianism
Classic utilitarians held hedonistic acts consequentialism. Consequentialism is the claim that an act is morally right if and only if that act maximizes the good, that is, if and only if the total amount of good for all minus the total amount of bad for all is greater than this net amount for any incompatible act available to the agent on that occasion. Hedonism then claims that pleasure is the only intrinsic good and that pain is the only intrinsic bad. Together these claims imply that an act is morally right if and only if that act causes “the greatest happiness for the greatest number,” as the common slogan says.
Classic utilitarianism is consequentialist as opposed to deontological because of what it denies. It denies that moral rightness depends directly on anything other than consequences, such as whether the agent promised in the past to do the act now. Of course, the fact that the agent promised to do the act might indirectly affect the act's consequences if breaking the promise will make other people unhappy. Nonetheless, according to classic utilitarianism, what makes it morally wrong to break the promise is its future effects on those other people rather than the fact that the agent promised in the past.

5. Consequentialism
What is Good? Hedonistic vs. Pluralistic Consequentialisms
From the start, the hedonism in classic utilitarianism was treated with contempt. Some argued that hedonism lowers the value of human life to the level of animals, because it implies that a simple game (such as tic-tac-toe) is as good as poetry if the game creates as much pleasure. Quantitative hedonists sometimes respond that great poetry almost always creates more pleasure than trivial games (or sex and drugs and rock-and-roll), because the pleasures of poetry are more certain, durable, fecund, and so on.

6. Pluralism about values also enables consequentialists to handle many of the problems that plague hedonistic utilitarianism.
For example, opponents often charge that classical utilitarians cannot explain our obligations to keep promises and not to lie when no pain is caused or pleasure is lost. Whether or not hedonists can meet this challenge, pluralists can hold that knowledge is intrinsically good and/or that false belief is intrinsically bad. Then, if deception causes false beliefs, deception is instrumentally bad, and agents ought not to lie without a good reason, even when lying causes no pain or loss of pleasure. Since lying is an attempt to deceive, to lie is to attempt to do what is morally wrong (in the absence of defeating factors).
Similarly, if a promise to do an act is an attempt to make an audience believe that the promiser will do the act, then to break a promise is for a promiser to make false a belief that the promiser created. Although there is more tale to tell, the disvalue of false belief can be part of a consequentialist story about why it is morally wrong to break promises.

7. Which Consequences? Actual vs. Expected Consequentialisms
A second set of problems for classic utilitarianism is epistemological. Classic utilitarianism seems to require that agents calculate all consequences of each act for every person for all time. That's impossible.
Most consequentialists claim that overall utility is the criterion or standard of what is morally right or morally ought to be done. Their theories are intended to spell out the necessary and sufficient conditions for an act to be morally right, regardless of whether the agent can tell in advance whether those conditions are met. Just as the laws of physics govern golf ball flight, but golfers need not calculate physical forces while planning shots; so overall utility can determine which decisions are morally right, even if agents need not calculate utilities while making decisions. If the principle of utility is used as a criterion of the right rather than as a decision procedure, then classical utilitarianism does not require that anyone know the total consequences of anything before making a decision.
Furthermore, a utilitarian criterion of right implies that it would not be morally right to use the principle of utility as a decision procedure in cases where it would not maximize utility to try to calculate utilities before acting. Utilitarians regularly argue that most people in most circumstances ought not to try to calculate utilities, because they are too likely to make serious miscalculations that will lead them to perform actions that reduce utility. It is even possible to hold that most agents usually ought to follow their moral intuitions, because these intuitions evolved to lead us to perform acts that maximize utility, at least in likely circumstances .

8. Consequences of What? Rights, Relativity, and Rules
 Another problem for utilitarianism is that it seems to overlook justice and rights. One common illustration is called Transplant. Imagine that each of five patients in a hospital will die without an organ transplant. A traveler is in the hospital for routine tests. Luckily (for them, not for him!), his tissue is compatible with the other five patients, and a specialist is available to transplant his organs into the other five. This operation would save their lives, while killing the “donor.” There is no other way to save any of the other five patients.
We need to add that the organ recipients will emerge healthy, the source of the organs will remain secret, the doctor won't be caught or punished for cutting up the “donor”, and the doctor knows all of this to a high degree of probability (despite the fact that many others will help in the operation). Still, with the right details filled in, it looks as if cutting up the “donor” will maximize utility, since five lives have more utility than one life (assuming that the five lives do not contribute too much to overpopulation). If so, then classical utilitarianism implies that it would not be morally wrong for the doctor to perform the transplant and even that it would be morally wrong for the doctor not to perform the transplant. Most people find this result abominable. They take this example to show how bad it can be when utilitarians overlook individual rights, such as the unwilling donor's right to life.

9. Deontological Theories
Having now briefly taken a look at deontologists' foil, consequentialist theories of right action, we turn now to examine deontological theories.
In contrast to consequentialist theories, deontological theories judge the morality of choices by criteria different from the states of affairs those choices bring about. The most familiar forms of deontology, and also the forms presenting the greatest contrast to consequentialism, hold that some choices cannot be justified by their effects—that no matter how morally good their consequences, some choices are morally forbidden. On such familiar deontological accounts of morality, agents cannot make certain wrongful choices even if by doing so the number of those exact kinds of wrongful choices will be minimized (because other agents will be prevented from engaging in similar wrongful choices).
For such deontologists, what makes a choice right is its conformity with a moral norm (Euthyphro). Such norms are to be simply obeyed by each moral agent; such norm-keepings are not to be maximized by each agent. In this sense, for such deontologists, the Right is said to have priority over the Good. If an act is not in accord with the Right, it may not be undertaken, no matter the Good that it might produce (including even a Good consisting of acts in accordance with the Right).

10. Agent-Centered Deontological Theories
According to agent-centered theories, we each have both permissions and obligations (duties) that give us agent-relative reasons for action. An agent-relative reason is an objective reason, just as are agent neutral reasons; neither is to be confused with the subjective reasons that form the nerve of psychological explanations of human action . An agent-relative reason is so-called because it is a reason relative to the agent whose reason it is; it need not (although it may) constitute a reason for anyone else.
Thus, an agent-relative obligation is an obligation for a particular agent to take or refrain from taking some action; and because it is agent-relative, the obligation does not necessarily give anyone else a reason to support that action. Each parent, for example, is commonly thought to have such special obligations to his/her child, obligations not shared by anyone else. Likewise, an agent-relative permission is a permission for some agent to do some act even though others may not be permitted to aid that agent in the doing of his permitted action. Each parent, to revert to the same example, is commonly thought to be permitted (at the least) to save his own child even at the cost of not saving two other children to whom he has no special relation. Agent-centered theories and the agent-relative reasons on which they are based not only enjoin each of us to do or not to do certain things; they also instruct me to treat my friends, my family, my promisees in certain way because they are mine, even if by neglecting them I could do more for others' friends, families, and promisees.

11. Patient-Centered Deontological Theories
A second group of deontological moral theories can be classified, as patient-centered, as distinguished from the agent-centered version of deontology just considered. These theories are rights-based rather than duty-based; and some versions purport to be quite agent-neutral in the reasons they give moral agents.
All patient-centered deontological theories are properly characterized as theories premised on people's rights. An illustrative version posits, as its core right, the right against being used only as means for producing good consequences without one's consent. Such a core right is not to be confused with more discrete rights, such as the right against being killed, or being killed intentionally. It is a right against being used by another for the user's or others' benefit. More specifically, this version of patient-centered deontological theories proscribes the using of another's body, labor, and talent without the latter's consent.
One finds this notion expressed, albeit in different ways, in the work of the so-called Right Libertarians, but also in the works of the Left-Libertarians as well. On this view, the scope of strong moral duties—those that are the correlatives of others' rights—is jurisdictionally limited and does not extend to resources for producing the Good that would not exist in the absence of those intruded upon—that is, their bodies, labors, and talents.

12. Just as agent-centered theories, so too do patient-centered theories (such as that forbidding the using of another) seek to explain common intuitions about such classic hypothetical cases as Trolley and Transplant (or Fat Man). In Trolley, a runaway trolley will kill five workers unless diverted to a siding where it will kill one worker. Most people regard it as permissible and perhaps mandatory to switch the trolley to the siding.
By contrast, in Transplant, where a surgeon can kill one healthy patient and transplant his organs to five dying patients, thereby saving their lives, the universal reaction is condemnation. The same is by-and-large true in Fat Man, where the runaway trolley cannot be switched off the main track but can be stopped before reaching the five workers by pushing a fat man into its path, resulting in his death.