Why do liberals and conservatives argue so much about morality? Don’t we all have a common sense of right and wrong?
Yes and no. For the common examples given by Christian apologists (torturing babies, for example), we’re all on the same page, but it’s more complicated than that. Psychologist Jonathan Haidt has brought the amorphous domain of morality into focus to reveal five separate categories. It’s a simple idea that explains much and can help us get past our differences—or at least understand them better.
From his TED video, here are Haidt’s five components of morality.

1. Care/harm. We’ve evolved to feel (and dislike) pain. This isn’t just true for ourselves; we also sense and dislike pain in others. From this comes kindness, nurturing, empathy, and so on.
2. Fairness/reciprocity. This is related to reciprocal altruism. From this foundation comes justice, rights, autonomy, and the Golden Rule.
3. Ingroup/loyalty. We have a long history as tribal creatures able to adapt to shifting coalitions. This foundation underlies patriotism, selflessness, and self-sacrifice for the group. It is active anytime people feel that it’s one for all, and all for one.
4. Authority/respect. As primates, we understand hierarchical social interactions. This foundation underlies the virtues of leadership and followership, including deference to legitimate authority and respect for traditions.
5. Purity/sanctity. This is shaped by the psychology of disgust and contamination. Being repulsed by things that look or smell bad can keep us from eating unsafe food. It also underlies religious notions of striving to live in an elevated, less carnal, and more noble way.

Haidt theorizes that the rise of civilization may have needed all five of the morality categories.
Make love, not war
Here’s the interesting bit: when people from different viewpoints are tested against these five categories, everyone strongly endorses #1 (care/harm) and #2 (fairness/reciprocity).
As Haidt’s drawing shows, Americans across the political spectrum strongly endorse the foundations of Care/Harm and Fairness. Not so for the next three. The conservative says “go team,” while the liberal says “celebrate diversity” (#3). The conservative says, “respect authority,” while the liberal says, “question authority” (#4). The conservative says, “life is sacred” (while the liberal says, “women have the right to choose”) and “Men kissing? Eww!” (while the liberal says, “Don’t like gay marriage? Don’t have one.”), category #5.
That’s a caricature, of course. Liberals like the team, authority, and purity as well; it’s just that they are likelier than conservatives to fear these good ideas taken to an extreme.
Liberals speak for the weak and oppressed, and they’ll risk chaos for the benefits of change. Conservatives speak for institutions and traditions, and they’ll risk injustice to those at the bottom for the benefits of order.
Haidt observes that in Eastern thought, it’s not the zero-sum game that it is in the West. While there are opposites (yin and yang, for example), they aren’t enemies. Each is recognized as having value. Brahma is the creator, Vishnu the preserver, and Shiva the destroyer. Each has a role.
This insight that morality is composed of different components has been helpful to me in making clear how those who disagree with me aren’t evil or insane but simply see morality differently. We value the same moral foundations but rank them differently.

See also: Understanding Morality—It’s Really Not that Hard

Are we at an impasse?
Let me think aloud for a bit.
Social liberals and conservatives will see issues like abortion and same-sex marriage differently. The liberal acknowledges the differences and wants each person to be minimally constrained. You need an abortion? Up to a point, it’s your choice. You’re going to get gay married? Congratulations!
Alternatively, if you don’t like abortion or gay marriage, then don’t get one. If you want to argue against them, the First Amendment allows that.
The conservative typically wants minimal government intrusion but makes an exception here because the stakes are so high. Life is too important to permit abortion. Marriage is too important in the traditional sense to expand the definition. Government is tasked to impose the correct approach on everyone.
Where does this put us as a society? Are we destined to struggle? Or are there larger social trends pushing us in one direction or the other where, like slavery and civil rights, one side will prevail and the debate will seem inconceivable decades from now?

Never let your sense of morals 
prevent you from doing what is right. 
— Isaac Asimov, Foundation

(This is an update of a post that originally appeared 5/29/13.)
Image credit: Wikimedia