I listened to this book as a follow up to Jonathan Haidt's excellent "The Righteous Mind." I didn't enjoy this book as much even though I probably would agree with Greene on more things than with Haidt. Haidt just had the advantage of going first and introducing me to the field of moral cognition. Greene is still a great read, and I recommend it to people even if they've already read Haidt.
This book centers around the quest for a universal moral currency that can adjudicate disputes between moral tribes, or the communities that the modern world increasingly throws into contact and conflict with each other. The book starts with the concept of the tragedy of the commons. In order for any community to work together, they need to mitigate the tragedy of the commons. Morality, in this evolutionary sense, is essentially a set of rules designed to facilitate cooperation within a group. However, we also have evolved, automatic settings that police our behavior from within, making us cooperative in the in-group almost by nature. We blush, gossip, get angry at taboo violators, have awe for the principles and sacred objects of the group, etc., and these automatic responses bolster (and are the basis of) the more abstract rules of humanity. Groups need this in-group harmony to survive, and the better they are at cooperation the more likely they are to survive.
So, the tragedy of the commons is solved! However, Greene says that this solution engenders its own new problem: the tragedy of common sense morality. When we meet other groups, we say "Hey, you guys don't do things like we do! What the heck! Let's fight." Each group's norms and values seem like "common sense" to the group, but they are nonsense (or worse) to the other group. Thus, Greene says we need a common language of morality
For that common language, Greene proposes happiness. It's something that we all agree that human beings should want. Ideally, we can put aside our common sense moralities and figure out what make human beings the happiest. Greene is a utilitarian in the spirit of Mill and Bentham, but he has drawn out a much more sophisticated version of utilitarianism than what most people associate with that term. Utilitarianism seeks the greatest good for the greatest number, but it also treats everyone's happiness as equally valuable. Slavery, for example, is not justified in utilitarianism because it makes some people a little happier but others a lot less happy. Greene argues that our debates about our ways of life should be based around figuring out what makes people the happiest without taking too much from any individual or group. Strangely enough, this reminds me a lot of Fukuyama's argument that liberal democracy is best at satisfying the individual's "struggle for recognition," dignity, and happiness.
In order to do this, Greene argues that we will have to rely much more on manual-mode, conscious reasoning to figure out what makes people the happiest. At this point he builds heavily on Kahneman and Tversky's Systems 1 and 2 arguments. Our automatic settings are too focused on in-group cooperation and out-group distrust, and they have a lot of weird biases to be reliable guides to inter-group disputes. For example, in the trolley problem, our automatic response is that pushing the person is wrong but pulling the switch is okay, even though they are the same result! Utilitarianism focuses on the outcomes rather than the inputs of these processes, helping us get closer to what ways of life work best in cases where we have to decide (abortion or gay marriage, for instance). I like the Greene puts more credence in our ability to consciously reason, whereas Haidt is a bit heavy on the point that our reasoning is just post hoc rationalization of our instincts.
One very interesting argument in this book is that the concept of rights aren't very good for settling tough inter-tribal disputes. Greene portrays rights as trumps: my right to speech, privacy, religion, etc trumps almost anything you can put against it. Rights claims are designed to end conversations about morality as final arbiters of what we can and can't do. However, in cases like abortion, rights-talk doesn't get us very far. One side says "right to life" and the other says "right to choose," but Greene says we don't get very far from those competing claims. You are likely to agree with the one from the tribe you come from, after all. Instead, Greene says that the common currency of happiness can help adjudicate these disputes. He concludes that outlawing abortion reduces happiness, especially the burden put on women, much more than it improves the happiness of somewhat theoretical lives, given that there's no scientific way to decide when "ensoulment" occurs. This is the pro-choice utilitarian argument that goes around the rights impasse.
Greene has a great section on why he's a liberal that successfully counters a lot of Haidt's arguments. Haidt argues that liberals have an impoverished moral palate. They are only sensitive to care/harm, fairness, and liberty arguments, whereas conservatives respond to these and other moral taste buds, including sanctity/defilement, authority/tradition, and loyalty. Haidt says that liberals have this problem because too many of their beliefs come from abstract moral reasoning, Enlightenment style, which is deeply disconnected from our social lives and evolutionary nature.
Greene's counterpoint is great: This removal from the common sense morality of one's tribe, this ability to reason more abstractly, is the core strength of liberalism. Unlike virtually any other code, liberalism strives to be a form of universal moral currency by basing its judgements not on what any given tribe finds to be right or wrong, but more objective measurements of happiness like harm and fairness. Liberalism arose from theorists like Locke, Mill, Bentham, Rawls, and others who were trying to figure out how to live peacefully and cooperate with different tribes than there own. They couldn't just command those tribes (other religions, peoples, etc) to obey their common sense moralities, so they had to figure out common principles that both sides could agree to: rights, balanced government, tolerance, the harm principle, equality, and fairness.
Social conservatism, in contrast, is in Greene's telling just a reflection of the common sense morality of each tribe. Do social conservatives value patriotism, sanctity, and tradition in the abstract, as Haidt claims? No: they value their own forms of patriotism, sanctity, and tradition. When Iranians rebel against their government, violating patriotism and respect for authority, American social conservatives rejoice. Social conservatives treat the traditions of other societies as wrong, weird, or sacrilegious, and, unlike liberal utilitarians, would never consider adopting those practices if they were proven to be more effective or better at generating happiness. If social conservatives value sanctity so much, why have so many of them been willing to desecrate the Qur'an, or support this kind of action? Why do they rejoice when Trump speaks of killing terrorists with bullets dipped in pigs blood? Social conservative movements operate from the common sense morality of "how we do things is how everyone else should do things, and our preferences should win out when they come into conflict with other tribes." This summarizes why Greene, and I, are liberals. I think we can see this point playing out right now in the great state of North Carolina.
I have two main problems with this book. First, I think the argument about rights is overstated. Greene doesn't really deal with the social contract aspect of liberal thought, which actually approaches rights from a fairly utilitarian perspective as well. Second, the book is a bit scattershot in its organization, and it has a little more philosophy than I wanted. Still, I recommend it highly to everyone. Yes, everyone! Moral cognition is an expanding field of moral psychology, and it cuts through so much BS and explains so much of our behavior that we should all at least engage with it.