Why do effective altruists support effective altruism?

Short answer: No consensus, but effective altruism is compatible with many views on morality, including consequentialism, contractualism, contractualism, deontology and virtue ethics.

Founder Will MacAskill wrote that effective altruism can rely on many morality theories

William MacAskill is an associate professor of philosophy at Oxford University. He’s been a pioneer in the effective altruism movement. And his most recent work argues that humanity should be thinking long-term as we make choices today. He is one of the originators of the effective altruism movement. In 2009, MacAskill, along with Toby Ord, co-founded the organization Giving What We Can, encouraging people to pledge to donate 10% of their income to effective charities. He co-founded the Centre for Effective Altruism in 2011 as an umbrella organization for Giving What We Can and 80,000 hours.

In his book, Doing Good Better, he claims that many of the ways people may think about doing good do relatively little, but that by bringing statistics and scientific reasoning to the generally emotive realm of doing good, possibilities to have a significantly bigger positive influence may be identified. He begins by presenting the argument that in selections with tradeoffs we can and should pick solutions that save more lives. He then makes this argument in a number of ways, from stating that giving to beneficial organisations may save much more lives than becoming a doctor, to making the case that Viktor Zhdanov, who spearheaded the elimination of smallpox in the Soviet Union was "the finest person who ever lived". MacAskill also addresses a number of instruments to make judgments like these, such as the disability-adjusted life year and the significance, tractability, and neglectedness framework (ITN framework).

MacAskill also discusses why fair trade does not significantly help the poorest farmers, why calling for a boycott sweatshops makes the whole thing worse for the global poor.  He provides the arguments that fair trade does not provide a feedback mechanism to determine if it is beneficial to the farmers involved, that while the situations in sweatshops may be terrible, the only possibilities for the people who work there are much worse, and that Wall Street bankers' salaries are so high that they could donate the salaries of multiple charity workers, thereby increasing their total number.

Peter Singer emphasizes that everyone's well-being counts equally

Peter Singer's ideas have contributed to the rise of effective altruism. In his book “The Most Good You Can Do”, released in 2015, the singer has written elaboratively on the moral imperatives for the reduction of poverty and elimination of suffering of non-human animals, with a special mention in the meat industry. Through his book, Peter shares his opinion on how the effective altruism movement is efficiently functioning towards achieving these objectives.

Peter singer is regarded as today’s foremost utilitarian. Peter freights the two available choices as good and bad based on his concept of moral theory - the theory of utilitarianism. Utilitarianism is the view that people should act so as to maximize the greatest happiness of the greatest number, and is regarded as one of the most influential moral theories of the last two centuries. The utilitarian approach demands that all individuals' interests be weighed equally. You may not regard the interests of certain individuals, including your own, more seriously than others. The utilitarian moral theory demands that moral judgements be founded on what Peter Singer refers to as the "equal consideration of interests." Utilitarianism moral theory involves the crucial notion that when calculating the utility of acts, regulations, or policies, we must do it without favouring ourselves, our friends, or those we care about most.

Singer argues that one should determine how to act by imagining a “happiness meter” that would measure the total, combined happiness of everyone before and after various events, and choose the course of action that yields the greatest sum of happiness. Good philanthropy, according to Singer, is the philanthropy that achieves the greatest “bang for the buck.”

Singer illustrates his point by contrasting the value of a $100,000 contribution to build an addition to a local museum with a $100,000 contribution to reducing the incidence of blindness in the developing world. On his account, this is a no-brainer: the contribution to reducing blindness is worth far more than the contribution to a local museum. Singer assumes that if we could measure everyone’s happiness with a happiness meter, it is certainly more happiness would be added to the global sum of happiness by preventing cases of blindness in the developing world rather than by building an addition to a local museum here in America. The only argument against Singer’s giving to the blindness-prevent program would be if some other, yet more efficient program came along.

He is a board member of Animal Charity Evaluators, a charity evaluator used by many members of the effective altruism community which recommends the most cost-effective animal advocacy charities and interventions. In particular, he expands upon some of the arguments made in his 1972 essay "Famine, Affluence, and Morality", citizens of wealthy countries are ethically compelled to donate a portion of their disposable money to organizations that aid the worldwide destitute, he argues. He supports this using the "drowning child analogy", which states that most people would rescue a drowning child from a pond, even if it meant that their expensive clothes were ruined, so we clearly value human life more than the value of our material possessions. As a result, we should take a significant portion of the money we spend on our possessions and instead donate it to charity.

Some believe that morality theories cannot be proven

People tend to develop their own understanding and views on morality over time based on their own set of interactions with individuals and social institutions. People belonging to different societies, cultures, upbringing, and other factors develop their different ideas concerning how humans are supposed to behave in different situations or circumstances, in a way that maximizes the collective well-being and reduce harm to human or non-humans. Different cultures and societies have their own rules, laws, and moral ideas majorly influenced by their religion and upbringing.

People believe that, unlike moral theories, scientific theories are tested, comprehensive, and supported by large bodies of converging evidence, based on repeated observations, usually integrating and generalizing hypotheses and making consistently accurate predictions across a broad area of scientific inquiry. Whereas on the other hand, moral theories are merely based on a person's personal perspective that differs from one to another. So these cannot be proven and their outcomes cannot be predicted.