"[Utilitarianism] means in its nakedness that in order to achieve the supposed good of fifty-one percent, the interest of the forty-nine percent may be, or rather, should be, sacrificed. It is a heartless doctrine and has done harm to humanity." 

From The Selected Works of Mahatma Gandhi 1968 , vol. 6 p. 230, ed. by Shriman Narayam

The most 'useful' ethical principle for considering the consequence of actions is that of utilitarianism - although in a very real sense it is not an ethical principle at all.

The general principle is usually only traced back to Jeremy Bentham in the eighteenth century, but in fact, in the Platonic dialogue the Protagoras, a suggestion is made that what is needed is the ability to weigh-up the pleasures against the pains likely to result from an activity. Jeremy Bentham's popularised the idea, saying that the right action is the one that brings about the greatest happiness of the greatest number - the general happiness is the best thing. John Stuart Mill (1806-73) adopted this theory and specifically rejected alternative moral theories as representing the interests of the ruling class, not justice. Those who taught the virtue of a life of sacrifice, Mill, wrote, wanted others to sacrifice their lives to them. Both Mill and Bentham say that people desire to be happy, and that this is actually the only thing they desire. When various peoples' desires conflict, the utilitarian theory weighs up the consequences and decides which action produces the greater happiness.

However, the Ancient Greeks could not agree on that. While some, like the astronomer Eudoxus, claimed that 'pleasure' was the sole good - (all other thing that we consider good are only because in some way they increase the amount of pleasure), Speusippus, on the contrary, held that pleasure (and pain) were two sides of the same thing- and that thing was evil. Utilitarianism thus is a way of maximising the amount of evil in the world!

Aristotle objected that utilitarianism neglects the virtue of character. In his Nicomachean Ethics he stresses instead that enjoying and hating the right things is the way to develop virtue of character. Neglecting the virtue of character in the blind execution of utilitarianism, as happening in our current world, makes a nation with the greatest number of people ignorant, prevail ignorance as the rule and leaving no room of living to those educated. This is a sign of a corrupted system where policy fails to maintain social order.

However, utilitarianism is flawed in many ways, Aristotle's view is just one criticism. In fact, utilitarianism is a kind of 'anti-ethics'. Its status as a kind of modern orthodoxy has many negative and cruel results, exemplified by the way it 'justifies' the violence with which the US and other 'developed' nations force their own interests upon the whole world.  

Asking us to accept the world as it is because this world is 'the best of all possible worlds' provokes many questions. To accept the world as it is as being the best possible, means accepting the evils in it as well. This raises the immediate questions: did God inject the evils in the world for us to accept them, live with them, and indeed spend our lives thanking Him for creating such a world? If the place and role of humankind as mandated by God is to live only to worship Him and pray till the end of our lives, then evil certainly serves a purpose, in making 'faith' more meaningful (difficult). Yet, if we were to fully accept the evils of the world as part of 'the best of all possible worlds', then, why struggle to improve things? If our work and labour offer to provide a better life, this implies that the existing world was not really the best possible after all, because it left room for improvements resulting from human efforts.

Efforts, for instance, to end wars, or ease natural disasters, or alleviate suffering.

It seems that if humanity were to fully embrace Leibniz's notion of this as 'the best possible world', no medicines would have been created to reduce mortality, and no efforts would be made to avert wars and natural disasters. Or, on a related theme, consider some political games of our times: particularly the game of claiming someone as being evil in order to give oneself the right to destroy them. Take the example of the U.S. invasion and subsequent occupation of Iraq. Over several decades, as many commentators have observed, the Iraqi president waged a pitiless war against his own people, with the active support of the United States government. Then, all of a sudden we found the US invading Iraq and executing its president claiming the actions as mandated by a struggle between 'good and evil'.

Of course, many countries have used such games in order to have the right to destroy or plunder enemies Nonetheless, there remains the fact that we do in practice seek and work for a better world in a world that is not, it seems, the best of all.