It is often claimed that moral values change greatly over time as societies “advance”. For instance, it is often claimed that modern societies are morally superior for not killing witches or shunning homosexuals. But perhaps what this apparent progress actually shows is that while we are scientifically superior, we may actually be morally similar, to ancient societies. Surprisingly similar moral values often underlie very different historical manifestations of morality. How can this be so? It seems to me that when we combine traditional moral values with increasing scientific knowledge, we actually get changes in cultural practices that are more just and compassionate. Let me unpack this with some thought experiments:
For instance, let us imagine that the Earth has been invaded by super-powerful, yet surprisingly inattentive, malevolent aliens. These aliens can overcome any human technology to kill humans, but they will only notice humans if they talk above a certain decibel level. If humans whisper, they are relatively safe from alien attack. Then let us say that a certain member of the human community decides that they are going to speak as loudly as they want "because it's their right". No reasoning can dissuade them, and if they are exiled they will tell the aliens where the other humans are. What would be the best course of action for the safety and well being of the community?
Obviously, the only solution is to kill the person (or otherwise traumatically end their ability to make sound) so they cease to be a threat to the community.
Let us take another situation: Let's say that we are the commander of a human colonization mission to another planet. Upon landing, the conditions are harsh, and the only way for the colony to survive is if each family has at least four children for the next several generations. Then let us suppose that we find there are several couples who are using birth control because they do not feel like having so many annoying children around them. What would be the best course of action for the safety and well being of the community?
Obviously, social sanctions, punishments, and incentives will need to be placed on these couples to keep up a fertility rate which will allow the colony to survive and thrive. Birth control will have to wait for a more comfortable and plentiful age in the colony's history.
In both of these examples, the moral value presupposed is the safety and well being of the community. And in both examples, fairly harsh punishments were needed to protect the community from actions which would not be punishable in other social circumstances.
When we look back in judgment on harsh punishments for witchcraft and homosexuality in human history, I would argue that it is not actually our moral values that have changed, but our level of scientific knowledge and economic development.
For instance, it was once thought that plagues and diseases and natural disasters were brought about by wicked spirits. And witches were people who sought to contact wicked spirits. And this was seen to endanger the whole community. These witches occupied the same role as the loud talking human during the alien invasion (above). And thus these witches were killed because they were thought to pose a clear and present danger to the community.
The reason why we don't kill witches anymore is not because we ceased to want to protect the community. The reason is because we no longer believe demons cause physical danger to the community, and thus it is silly to kill witches for trying to contact demons. If we still believed in demon caused disasters, we would still kill witches just as sure as we would kill the loud talker during the alien invasion.
Likewise, the social sanction against homosexual behavior in most ancient societies probably originates in the need for those societies to be fertile in order to survive and thrive and conquer rival tribes. When societies live near subsistence level, children are not only beloved offspring, but also a real source of labor and social support. And because of infant, childhood, and adult mortality, it is necessary to have broods of kids just to "break even". So, those who do not contribute to the breeding and rearing of lots of children will need to be incentivized and/or punished to be as fruitful as possible. At least until society reaches a level of comfort and productivity.
Notice that it is the same moral value-- the safety and well being of society-- that animates the killing of loud talkers and witches, and the shunning of birth control users and homosexuals.
But when society reaches new levels of comfort, productivity, and scientific knowledge, the same moral value-- the safety and well being of society-- animates very different moral behaviors.
For instance, once we realize that demons do not cause disasters, and that religiously based hatred and persecution actually tears apart the social fabric of communities, we stop persecuting witches. Why? Because we realize that labeling and hatred based on religion actually perpetuates a cycle of oppression that lowers living standards for all in the community. So, based on new scientific knowledge, tolerance and inclusion take the place of killing witches because of the SAME moral value which caused us to kill witches in the first place.
In a similar way, once a society reaches a certain level of development, fertility is no longer as important. In fact, high fertility rates can actually increase poverty in some demographics in urban modern societies. Thus, in order to increase the overall wellbeing and health of society, birth control and homosexuality could be seen as moral goods, because they allow people to have healthy and fulfilling lives without contributing to overpopulation. In addition, we also come to realize that persecution based on gender or sexuality actually decreases the overall wellbeing and social cohesion of society. An advanced society that is compassionate and inclusive allows for full human flourishing in a way that a society filled with hate and oppression does not.
And notice that moral values have not changed. The moral value in both primitive and advanced societies is the safety and well being of society. But how this moral value is lived out is completely opposite depending on the level of development in society. In a primitive society, birth control and homosexuality are heavily sanctioned; In an advanced society, they are permitted and even celebrated; All based on the same moral value.
Now this does not mean that there is no moral progress across history. There are some cases of real moral progress in society. But even in these cases, increasing scientific knowledge plays a large part.
For instance, we see a tendency in older societies for certain ethnicities of male to treat women and other ethnicities as property, alongside livestock and material goods. And we rightly say that it is moral progress that we now treat women as full citizens and no longer allow slavery. But even this is predicated on a change in scientific knowledge. All functioning societies have taught that "humans ought to be treated with dignity and respected and not treated as property". But the catch is that many ancient (and not so ancient) societies found reasons to say that certain kinds of people were not as fully human as adult male humans of a certain ethnicity. Women were seen as incomplete humans, only made complete by being connected to a male householder (whether a father or husband). Other ethnicities were seen as deficiently human or sub-human, and thus able to be bought and sold as slaves.
It was only when scientific knowledge effectively destroyed the idea that there was some kind of qualitative difference between male and female intellectual abilities, or between the abilities of different ethnicities, that we came to realize that we are all fully human and deserve full human rights. And note it wasn't that the moral value changed that "all humans should be treated with equal dignity". This value has stayed the same in most societies. What changed is that our understanding of who is fully human has greatly enlarged due mainly to scientific knowledge.
This increased understanding that all humans are fully human and worthy of full human rights also contributes directly to why we don't burn witches or sanction homosexuals anymore. Their persecution in pre-modern societies not only stems from the concerns raised above, but also because they were members of classes of humans that were considered to be deficient or abnormal humans, and thus not fully human, and not fully worthy of respect and dignity. But we have come to realize that not only are women fully human, but also women who practice different religions (i.e. witchcraft) are fully human. And we have come to realize that homosexual orientation is not "abnormal", but part of the normal distribution of sexual orientation in most advanced mammals.
Thus, because of increased understanding, we have come to see that full humanity resides in women, religious others, ethnic others, and LGBT persons. And because they are all now seen as fully human, we apply the ancient moral value "all humans ought to be treated with respect and dignity" to them as well. Again, the moral value didn't change. What changed is the set of people to whom we apply that moral value to.
I will end by saying that I think there is moral progress in history. It just isn't as clean cut, nor as obvious, as some might make it seem. Most of our moral progress seems to stem from increased knowledge of ourselves and our world, and not because our core moral values have actually changed over time. When we remember that, it is much easier to see how the same moral values underlie diverse moral behaviors across history, and how we can combine these traditional values with new scientific knowledge to make our world a more just and compassionate society to live in.