On Wednesday, President Obama called on Americans to “expand our moral imaginations, to listen to each other more carefully, to sharpen our instincts for empathy, and remind ourselves of all the ways our hopes and dreams are bound together.” Those were beautiful words; they spoke to our desire for reconciliation.

But the truth is that we are a deeply divided nation and are likely to remain one for a long time. By all means, let’s listen to each other more carefully; but what we’ll discover, I fear, is how far apart we are. For the great divide in our politics isn’t really about pragmatic issues, about which policies work best; it’s about differences in those very moral imaginations Mr. Obama urges us to expand, about divergent beliefs over what constitutes justice.

And the real challenge we face is not how to resolve our differences  something that won’t happen any time soon  but how to keep the expression of those differences within bounds.

What are the differences I’m talking about?

One side of American politics considers the modern welfare state  a private-enterprise economy, but one in which society’s winners are taxed to pay for a social safety net  morally superior to the capitalism red in tooth and claw we had before the New Deal. It’s only right, this side believes, for the affluent to help the less fortunate.