I think the best starting place for understanding pluralism is humility as a virtue. Not a humility that despairs of improving our knowledge about ourselves and the world, but one that acknowledges our deep fallibility and finitude. For example, no one has ever had the chance to think through all the consequences of his or her beliefs, and we do not even possess the requisite background knowledge to carry it out. Pluralism then easily arises from recognizing how we are “rational satisficers,” to use Herbert Simon’s term, i.e. people who are constrained in achieving their aims due to imperfect information and limited resources for deliberating on our choices. In the context of finite time and incomplete knowledge, it is often impossible to demonstrate that one decision method is absolutely better than another: we cannot find the universal standard by which to compare the methods, and we cannot achieve absolute precision in marking off the domain of each method’s superiority.
Think, for example, of the problem of finding the most efficient route for a traveling salesman to cover all his destinations. There is no practical and optimal search algorithm for finding this best pathway. The alternatives, i.e. heuristic procedures, typically possess both strengths and weaknesses that make them better suited to some contexts and not to others. But knowing which context is which is itself a difficult problem, and in many cases researchers or engineers have to compare the results of multiple methods empirically on a standardized data set without an absolute standard.
Problems in philosophy are often at least this difficult. In fact, many philosophical debates center on the logically prior problem of defining what “the best option” or “optimal” means. In this case, the humility appropriate to pluralism would concede that there is no guaranteed way of knowing which understanding of “best” is “best” in advance. Instead, this evaluation must be carried out iteratively, comparatively, and contextually. Being a pluralist means always being willing to deliberate over the alternatives and to recognize that alternatives that are unacceptable now may, upon further investigation, turn out better than they first appeared. A pluralist draws a further consequence from this fact, which is that one should commit to supporting multiple alternatives, even if one believes some of them are wrong at any given time.
However, pluralism does not require one to treat all alternatives as equal or to say that no comparative judgment is possible. Rather, pluralism insists on the long-term positive value of alternative approaches to a problem, based on a recognition of the fallibility and incompleteness of one’s own position. Pluralism therefore does not simply equate with “inclusion.” Any alternative does not merit inclusion (or institutional support in some form) simply because it surpasses some basic threshold. Rather, the alternatives merit a level of support because they may turn out better than our own point of view. On a higher level, a pluralist would recognize how his or her own perspective consistently gains from having to engage with alternatives, and that no single perspective may ever prove adequate to whatever issue is at hand.
In this regard, most researchers in academia would recognize themselves as pluralists in certain respects. But a thorough-going pluralism brings this stance of humility to all levels of inquiry and action. For example, take a problem like determining the just distribution of resources for health care. One level of pluralism would be to value the contributions of philosophers proposing different analyses within a single moral tradition such as utilitarianism. This is a narrow pluralism compared with also valuing the contributions of other philosophical traditions, such as virtue ethics or a Rawlsian approach. “Valuing” can mean supporting or at least not strongly opposing philosophers working in the other tradition, and it can also mean actively trying to learn from them and incorporate the best of their work into your own tradition. A thorough-going pluralism applies to methods as well as competing solutions within a method. One could say something similar for analytic, continental, and non-Western traditions in philosophy.
In this light, it turns out that thorough-going pluralism is far from vacuous; in fact, it is quite difficult. One must commit to the idea that everything one holds dear could be radically wrong. Recognizing this skepticism does not negate our cherished beliefs, but it does place them in some degree of uncertainty between absolute truth and falsity, or absolute superiority and inferiority. Such a conception of pluralism is not limited to academia and research, but is possible to extend to life more generally. In a democracy, it can mean recognizing that each person is responsible for their own pursuit of happiness (or other good), and that we should be humble in our own pursuit by recognizing that what we believe is good may turn out to be wrong, and that other people, whom we initially conceive of as our opponents, may become our best teachers.
In this understanding, inclusion is something that pluralism broadly encourages, but inclusion itself is not conceptual heart of pluralism, which lies in a recognition of our own deep fallibilty. Just because everyone in a conversation may agree that pluralism is a good thing does not mean we have nothing to argue about. The issue at hand is precisely to what extent our aims as a group are served in the long run by supporting alternative positions, methods, attitudes, and so forth. This is not a problem we can adjudicate in a priori fashion — but that doesn’t mean it’s not substantive! Rather, our discussion hinges on the nature of our collective aim, what believe are the relevant costs of including conflicting points of view in the group, and the potential benefits. It may be, for example, that we would like to be more inclusive but that the group is fragile and more tension would likely cause it to fall apart. In this situation, we must realize that practical constraints have prevented us from being as thorough-going in our pluralism as we would ideally prefer. This neither contradicts our ideal nor erases the fact that we have achieved some level of pluralism, even if it falls short of our standards.