In an influential book of ethics first published in 1981, the philosopher Peter Singer offers a striking image of moral progress over the course of human history: an expanding circle of moral concern, beginning with our own family or tribe, and expanding over time to include larger groups, nations, families of nations, all humans and perhaps even nonhuman animals.
With our evolved cognitive capacities and the help of increasingly sophisticated reasoning, we can come to appreciate how and why the scope of our moral concern should grow.
The details of Singer's position are controversial, but the idea of an expanding circle of moral concern is widely accepted among those who endorse moral progress — the idea that over time, we develop better ethical theories and more ethical practices. As expressed in a quote attributed to Martin Luther King Jr.: "The arc of the moral universe is long, but it bends toward justice."
Moral progress is an easy idea to embrace, but it's not an easy idea to defend. What, after all, is the force that ensures we move in the right direction?
As individuals, we are eminently fallible, prone to focusing on our own concerns. As a country, we face new challenges about how to define ourselves as a nation, and how to understand our role in the world.
I can only hope that the circle continues to expand. I cannot speak for other Americans, but I can speak for myself.
To Muslims and to Jews I say: You are in my circle.
To women and to people of color I say: You are in my circle.
To members of the LGBTQIA community I say: You are in my circle.
To immigrants and to refugees I say: You are in my circle.
To people with disabilities I say: You are in my circle.
To readers I say: You are in my circle.
When it comes to moral progress, there are no guarantees. It's up to us to treat each other well and to make the best decisions for our generation and for those to come.
Tania Lombrozo is a psychology professor at the University of California, Berkeley. She writes about psychology, cognitive science and philosophy, with occasional forays into parenting and veganism. You can keep up with more of what she is thinking on Twitter: @TaniaLombrozo