How do Secular Humanists develop their ethics? This is the most consistently repeated question about Secular Humanism. Theists, in particular, have difficulty with the notion that ethics need not come from a set of rules laid down in an ancient book. Even Secular Humanists, put on the spot, have some difficulty giving a clear and convincing answer. Often they are stuck saying, "Well, we just are moral."
Secular Humanists actually develop ethics using three characteristics of human beings: a kind of ethical tripod, if you will.
The first of these characteristics is a trait that evolved in all vertebrate species, a long time ago. When primates do something positive for fellow primates, their brains get a little charge of dopamine. Apparently, this happens in all vertebrates, but for some reason seems more pronounced in primates. This chemical gives pleasure so ancient human ancestors tended to do positive things for each other because of this reward even though they did not understand it. Modern neurological research supports this idea in both human and non-human primates.
The effect of this trait for human beings is that they are social, preferring to work positively with others and to co-operate in positive social ways.
The second of these characteristics, tribalism, is also an evolved trait. It, too, is present throughout the primate family, although it seems somewhat diminished in bonobos. Tribalism is the tendency to form small groups or sets of primates that co-operate with members of the same tribe, but not so much with other tribes
Tribalism seems to be the result of finite limits to food resources for foragers and hunter-gatherers. Without the science of cultivation to enhance food production, ancient human ancestors needed a minimum area for foraging and, later hunter-gathering. This, combined with relatively limited ability to travel long distances, also tended to isolate social groups geographically. This tribalism continues in modern ape species. Chimpanzees, for example, are very tribal with well establish territories. Their tribes often get into serious conflict along the borders of adjoining territories. Sound familiar?
This trait, then, in its extreme form, is a negative characteristic that can cause real conflict between different tribes. In the modern world, human beings use different terms for tribes-nations, churches, clubs, and so on, but these entities retain most of the characteristics of tribes.
There are, then, two seemingly opposing instincts: dopamine addiction and tribalism. How can Secular Humanists claim to develop ethics or moral codes from that teeter-totter?
Enter the third, predominantly human, characteristic, reason. Human beings have the most highly developed ability to reason on the planet (until cetaceans mount a good lobby group). Sophisticated human language skills, including the tendency to think in word form as well as communicate with each other give human beings considerable control over the first two traits.
This third characteristic allows human beings to balance the two other characteristics. Yes, balance is necessary. One might think that human beings would be better off abandoning tribalism completely.
However, without it, dopamine pursuit would lead to gullibility and make human beings very vulnerable. Pulling a thorn out of a lion's paw is a noble idea, but in a purely dopamine-driven psychology very dangerous without the due caution one would need to pull it off -- sorry out.
Controlled tribalism serves a purpose. It makes human beings sufficiently wary of unknown people and circumstances to reduce their vulnerability. This is the basis of the street smarts that help a child resist helping the stranger to look for the puppy.
When reason fails, either dopamine pursuit or tribalism takes over. The result is that human beings become either victims or predators and ethics go out the window. That is essentially what happens if tribalism is strong enough to give someone a dopamine response from following a dogma without the balance of reason.
Secular Humanists use reason to develop ethical guidelines balancing the dopamine reflex and tribalism to make moral decisions. This isn't necessarily easy and not always successful, but the technique works at least as well as the technique of following a fixed set of rules set down in the past, often with tribalism as the predominant consideration.
Secular Humanists do not rely on a dogma-based answer to an ethical question, but will take time to apply reason to make the best possible decision under the circumstances present.