There seems to be a widespread and misconceived belief that the biggest problems in the world are caused by hatred. However, if we miraculously got rid of all the hatred in the world tomorrow, the worst problems would remain. 
All the major causes of suffering in the world seem to be the result of the absence of caring (i.e. indifference), rather than the presence of hatred:
1. Extreme poverty is not the result of the rich hating the poor; its continued existence is the result of the rich being largely indifferent towards the suffering associated with extreme poverty.
2. Factory farming is not the result of human hatred towards non-human animals; it is the result of human indifference towards the intense suffering of animals living in intense confinement.
3. Humanity's collective under-investment in the prevention of existential risks, which endanger the existence and flourishing of our future descendants, is not the result of the present generation hating future generations; it is the result of the present generation being largely indifferent towards the well-being of potential future lives, of which there could be an astronomical number.
4. The widespread and intense suffering of animals living in the wild is not the result of hatred; it is the result of a blind and indifferent optimization process (i.e. evolution through natural selection).
Indifference is the immediate result of our evolved human cognitive architecture that is largely insensitive to the scope of moral problems and to the well-being of those different from ourselves, as demonstrated by the work of Paul Slovic.
The problem of indifference is not solvable merely by increasing emotions such as love or empathy, despite their importance in our everyday lives. These emotions are too narrow and parochial to reliably extend to all beings that deserve our moral concern. In Joshua Greene's words, our "emotions make us social animals, turning Me into Us. But they also make us tribal animals, turning Us against Them". Heightened empathy and love are important drivers for in-group altruism, but by themselves they are not sufficient to overcome our collective indifference—especially, because they may in some cases actually increase bias and hostility towards the out-group. In the same vein, Paul Bloom points out that
"I actually feel a lot less empathy for people who aren’t in my culture, who don’t share my skin color, who don’t share my language. This is a terrible fact of human nature, and it operates at a subconscious level, but we know that it happens. (...) empathy often leads us to make stupid and unethical decisions. (...) when it comes to moral reasoning, empathy (...) just throws in bias and innumeracy and confusion."
The fact that to a human brain ten deaths feel only marginally less bad than one thousand deaths is merely a fact about our state of mind, not about the world itself. The badness of the suffering of others is not in the least alleviated by the fact that we are largely indifferent towards it, whether by our choice or by our nature. Joseph Stalin is reported to have said, "A single death is a tragedy; a million deaths is a statistic". Yet, embracing our brain's capacity for deliberate reasoning, we can truly make a step towards overcoming our indifference—recognising that while every single death is indeed a tragedy, a million deaths really are a million tragedies.
In other words, what is needed to address the problem of indifference is, as Bloom puts it, that we should "in the moral domain, (...) become rational deliberators motivat[ed] by compassion and care for others." Relatedly, Robin Hanson comments that "if only we could be moved more by our heads than our hearts, we could do a lot more good." This is almost precisely how Peter Singer described effective altruism in its early days in his 2013 TED talk, stating
"[effective altruism is] important because it combines both the heart and the head. The heart, of course, you felt (...) the empathy for that child. But it's really important to use the head as well to make sure that what you do is effective and well-directed; and not only that, but also I think reason helps us to understand that other people, wherever they are, are like us, that they can suffer as we can, that parents grieve for the deaths of their children, as we do, and that just as our lives and our well-being matter to us, it matters just as much to all of these people".
To overcome our collective indifference towards the largest causes of suffering, Singer suggests that we need to use our reasoning faculties to accept a notion of impartiality as fundamental in our concern for others and to let this insight guide our altruistic decision-making and actions: the insight that the suffering and well-being of myself and my tribe is not intrinsically more important than that of yourself and your tribe.
Impartiality is most crucial when our emotional indifference is most inadequate—when we are dealing with the suffering of those most distant to ourselves. Yet, as Singer's idea of the expanding circle illustrates, moral impartiality can transcend geographic, temporal and even species-based boundaries. It was the application of this impartiality principle that put Jeremy Bentham so far ahead of time, with regards to his contemporaries, writing
"Why should the law refuse its protection to any sensitive being? (...) The time will come when humanity will extend its mantle over everything which breathes (...) when the rest of the animal creation may acquire those rights which never could have been withholden from them but by the hand of tyranny."
The ongoing moral catastrophes of our time—extreme poverty, factory farming, existential risks etc.—illustrate that even centuries after Bentham's death there remain numerous neglected opportunities to do an enormous amount of good. These are opportunities to, as Singer puts it, "prevent something bad from happening, without thereby sacrificing anything of comparable moral importance". Using evidence and reason, effective altruism is the intellectual pursuit and practical implementation of these opportunities.
Or, to put it differently: effective altruism is the serious attempt to overcome our collective indifference towards the major causes of suffering in the world.
In addition to providing benefits such as improved coordination, the effective altruism community serves this purpose in two important ways: First, it increases the altruistic motivation of its members over the long-term by connecting them with other individuals, groups and organisations with shared goals and epistemic norms, thus overcoming feelings of isolation in their pursuit to do the most good. Second, the EA community establishes social incentives that reward altruistic actions aimed at benefiting others the most, as opposed to altruistic actions that mainly serve to foster our own (hidden) selfish motives. The 'warm glow' theory of giving in economics suggests that many people donate money or volunteer (in part) to reap the emotional satisfaction associated with helping others, often choosing emotionally salient causes over other more effective causes—in contrast, the EA community increases the positive impact of its members by positively reinforcing effectively altruistic decisions (e.g. by systematically comparing cause areas, choosing charities based on rigorous cost-effectiveness evaluations etc.). To this end, Robin Hanson argues that
"to put ourselves in situations where our hidden motives better align with our ideal motives (...) we might join the effective altruism movement, in order to surround ourselves with people who will judge our charitable giving more by its effects than by superficial appearances. Incentives are like the wind: we can choose to row or tack against it, but it’s better if we can arrange to have the wind at our backs."
At the same time, the ideas and principles of effective altruism help to overcome indifference on an intellectual level. For instance, Nate Soares writes that
“if you choose to do so, you can still act like the world's problems are as big as they are. You can stop trusting the internal feelings to guide your actions and switch over to manual control. (…) addressing the major problems of our time isn't about feeling a strong compulsion to do so. It's about doing it anyway, even when internal compulsion utterly fails to capture the scope of the problems we face. (...) The closest we can get [to comprehending the scope of these problems] is doing the multiplication: finding something we care about, putting a number on it, and multiplying. And then trusting the numbers more than we trust our feelings."
For some people, the rational and systematic approach to doing good taken by effective altruism may at first feel cold and calculating. However, effective altruism really is warm and calculating. Behind every number there are individuals that matter. Prioritising who to help first is the warm-hearted response to the tragically indifferent world we live in; a world where the resources of those who care are far too limited provide for everyone deserving of being cared for.
“I fervently hope that one day we will be able to save everyone. In the meantime, it is irresponsible to pretend that we aren’t making life and death decisions with the allocation of our resources. Pretending there is no choice only makes our decisions worse. (...) I understand that it’s hard, that we will always instinctively care more for the people we see than those we don’t. (...) But there should be great shame in letting more people suffer and die than needed to because you can’t look past your own feelings."
Ending on the words of someone who fought humanity's collective indifference for most of his professional career, deceased statistician Hans Rosling wrote:
“It is hard for people to talk about resources when it comes to saving lives, or prolonging or improving them. Doing so is often taken for heartlessness. Yet, so long as resources are not infinite—and they never are infinite—it is the most compassionate thing to do to use your brain and work out how to do the most good with what you have.”
I owe my gratitude to Chi Nguyen, Nadia Mir-Montazeri, Eli Nathan and Huw Thomas for providing me with valuable feedback on this post.
: Stefan Schubert commented on an earlier version of this post: "I agree with much of this. However, [I] guess that morally motivated hatred presents large opportunity costs: people focus on hating their moral opponents, and on zero-sum conflicts with them, rather than on finding effective solutions. Hatred is also probably a reason why people don't engage more in moral trade and moral cooperation."