Why is it wrong to enslave or torture other humans, or take their property, or discriminate against them? That these actions are wrong, almost no one disputes. But why are they wrong?

For an answer, most people turn to religion (because God says so), or to philosophy (because rights theory says so), or to political theory (because the social contract says so). In The Moral Arc, published in January, I show how science may also contribute an answer. My moral starting point is the survival and flourishing of sentient beings. By survival, I mean the instinct to live, and by flourishing, I mean having adequate sustenance, safety, shelter, and social relations for physical and mental health. By sentient, I mean emotive, perceptive, sensitive, responsive, conscious, and, especially, having the capacity to feel and to suffer. Instead of using criteria such as tool use, language, reasoning or intelligence, I go deeper into our evolved brains, toward these more basic emotive capacities. There is sound science behind this proposition.

According to the Cambridge Declaration on Consciousness—a statement issued in 2012 by an international group of prominent cognitive and computational neuroscientists, neuropharmacologists and neuroanatomists—there is a continuity between humans and nonhuman animals, and sentience is the most important common characteristic. The neural pathways of emotions, for example, are not confined to higher-level cortical structures in the brain but are found in evolutionarily older subcortical regions. Artificially stimulating the same regions in human and nonhuman animal brains produces the same emotional reactions in both. Attentiveness, decision making, and the emotional capacity to feel and suffer are found across the branches of the evolutionary tree. This is what brings all humans and many nonhuman animals into our moral sphere.

The arc of the moral universe really is bending toward progress, by which I mean the improvement of the survival and flourishing of individual sentient beings. I emphasize the individual because that is who survives and flourishes, or who suffers and dies, not the group, tribe, race, gender, state or any other collective. Individual beings perceive, emote, respond, love, feel and suffer—not populations, races, genders or groups. Historically, abuses have been most rampant—and body counts have run the highest—when the individual is sacrificed for the good of the group. It happens when people are judged by the color of their skin, or by their gender, or by whom they prefer to sleep with, or by which political or religious group they belong to, or by any other distinguishing trait our species has identified to differentiate among members instead of by the content of their individual character.

The rights revolutions of the past three centuries have focused almost entirely on the freedom and autonomy of individuals, not collectives—on the rights of persons, not groups. Individuals vote, not genders. Individuals want to be treated equally, not races. In fact, most rights protect individuals from being discriminated against as individual members of a group, such as by race, creed, color, gender, and now sexual orientation and gender preference.

The singular and separate organism is to biology and society what the atom is to physics—a fundamental unit of nature. The first principle of the survival and flourishing of sentient beings is grounded in the biological fact that it is the discrete organism that is the main target of natural selection and social evolution, not the group. We are a social species, but we are first and foremost individuals within social groups and therefore ought not to be subservient to the collective.

This drive to survive is part of our essence, and therefore the freedom to pursue the fulfillment of that essence is a natural right, by which I mean it is universal and inalienable and thus not contingent only on the laws and customs of a particular culture or government. As a natural right, the personal autonomy of the individual gives us criteria by which we can judge actions as right or wrong: Do they increase or decrease the survival and flourishing of individual sentient beings? Slavery, torture, robbery and discrimination lead to a decrease in survival and flourishing, and thus they are wrong. QED.