But perhaps the fat man should not be pushed, even to save five other lives.
We can all agree that killing people (except in self-defense) is inherently wrong. So, if we analyze the action itself--the act of killing the fat man--rather than the end of the action--the act of saving lives--we reach radically different conclusions.
It is a moral principle that we should not kill others. Arguably, this principle stands even in the difficult scenario at hand. Perhaps some principles are so fundamental that they must be adhered to in all cases. What principle could be more fundamental than the prohibition against killing? The argument just advanced is a non-consequentialist one. It focuses on the act of killing, rather than the consequences of killing. This type of argument, where the morality of an action is based upon the action itself rather than the effect of the action, is non-consequentialist.
The non-consequentialist conclusion that the fat man ought not be killed is based upon the principle that taking human life is immoral. But how do we arrive at this principle? The philosopher Immanual Kant held that people possess moral worth, or human dignity, because of their ability to make autonomous choices based upon rationality. In other words, people are not tools to be used for various purposes but instead are valuable in and of themselves. In fact when we treat people as mere tools, we violate their human dignity. Kant held that people should not be treated as means to ends. This requires that we should not use people as instruments to bring about effects which we desire. To shoot the fat man would be to use his life as a means to an end--the preservation of other lives.
Kant's principle that people should not be treated as means to ends may be called the Categorical Imperative. The prohibition against using people as means to ends applies in all cases--it is categorical. Even if using people as a means to an end furthers important principles, it cannot be justified because it is inherently immoral. More generally, the Categorical Imperative means that actions are moral or immoral in and of themselves and not because of the ends they bring about in specific cases.
According to Kant, because killing people is immoral generally, it is immoral in the specific case as well. If everyone accepted the principle that killing were just, the effects would be disastrous. Therefore, according to Kantian, Categorical Imperative analysis, the fat man should be spared based upon the principle that killing people is wrong no matter what the context.