One takeaway from the study of ecology is that the interdependence of species in an ecosystem can lead to counterintuitive outcomes from changes in populations. For example, we might intuitively expect a fall in predator populations to entail an increase in the population of their prey. And while this may be true in the short term, in the longer term the story is more complicated, and often includes a fall in prey populations as well. The outdated idea of a food chain can lead us to believe that predators sit atop a hierarchy, and all effects flow downward. In fact, predator and prey are both nodes in a more complicated food web, so that changes in the population of any species will have rippling effects across other species.
Another takeaway is that a diversity of species benefits an ecosystem. For example, the reintroduction of wolves to Yellowstone benefited numerous other species, from willow trees that had been overgrazed by the elk wolves prey on, to beavers (that use the willow to build dams), mice (that live in reinvigorated willow stands) foxes and raptors (that prey on mice and beavers), grizzly bears and ravens (that scavenge the leftovers of wolf kills), and arguably even the elk themselves (whose sick are thinned, and whose food supply and population is more stable).
What might we learn by applying a similar type of thinking to morality? As I’ve argued elsewhere, moral systems are an evolutionary strategy. But moral systems are diverse in the modern world, and so they evolve not only on their own, but in relation to and in dependence upon the moral systems around them.
A historical example might be having multiple religious communities living near each other. This may enable members of one faith to obtain services that they are prohibited to perform themselves, or to carry out services that they are prohibited to perform on their coreligionists. While these types of services are often derided, they have been an important part of development and social cohesion in many parts of the world, providing much needed slack in systems of rules that by their nature are generally not seen as flexible.
Another example might be holding different classes of people within a society to different standards. Many societies have had a warrior class, whose members were subject to different rules that were arguably moral in nature (e.g. various bushido codes that gave privilege and permission to their followers, but also put significant demands on them). Encouraging different sets of rules for these people may benefit the ‘ecosystem’ of the community, in that they maintain a disciplined class who perform a vital service.
The consequences of this view are strange and somewhat repugnant to the modern liberal idea of equality before the law, because they seem to suggest that, not only are different moral conclusions on the same action consistent, having differing moral systems may actually be beneficial to the community as a whole. It’s intuitively plausible that too uniform a moral system may introduce vulnerabilities. For example, consider guerrilla warfare, which often involves members of different moral systems: smaller groups can often find unexpected success by employing tactics that are unthinkable to their larger adversaries; because common knowledge dictates that one does not cross certain moral lines, they are caught off guard by forces that do.
A possible further direction of inquiry would be to determine if it is possible to find a meta-moral system that could govern a pluralistic society in this way, or if that project is always doomed to either wipe out all systems but one, or merge all the system into a single, vulnerable common code (David Friedman’s Legal Systems Very Different From Ours chapter on “Embedded and Polylegal Systems”). Alternatively, one might ask whether and where we should in general ignore this even if it’s true, as asserting the unique truth of a particular moral system is a necessary part of the dynamic that makes the ecosystem work, as wolves must eat elk as part of a healthy food web.