One term that gets thrown about a lot to the point of serious abuse is “rationality.” Often, accusation of “irrationality” is thrown about to indicate denigration towards “the other,” while many pride themselves in how “rational” they are. Postmodernists have taken this to the other absurd extreme, by denying that there is anything called rationality and declaring all manner of beliefs as simply constructions that are equally valid, regardless of how absurd they might be.
Thomas Kuhn approached this problem from the perspective of someone who had a foot in both worlds, a humanities scholar who was trained originally as a rigorous scientist. His conclusion that undergirds The Structure of Scientific Revolutions is that what is “rational” is simply a set of logically consistent beliefs that are also compabible with the observed reality, within the degree of precision given the available technology of the time. (Not necessarily in so many words, perhaps, but one might remember that, while describing the Support Vector Machines and the motivating logic behind statistical learning in general, Vladimir Vapnik invoked the philosophy of science to explain what is and what is not learnable from the observed data–which, in turn, comes from a long tradition of mathematical philosophy.)
This implies a perfectly “rational” reasons between a disagreement, even in face of a common observation. The disagreeing parties could easily have fully logically consistent set of beliefs about how the world operates that can account for all the observed reality. They agree on the facets of reality that they see, but they do not agree on how they arrived at it, and there is no way to tell one explanation is more right than the other, or indeed, if there is a more “right” explanation. This is not a new observation, of course: as a trained physicist, I wonder if Kuhn was channeling Einstein’s famous thought experiment about the equivalence principle.
A simple explanation of the equivalence principle is illustrated at this web page, but the point for us is even more elementary: there are times when no experiment, however cleverly they might sidestep the laws of physics, it is impossible to distinguish between explanations X and Y because, for all intents are purposes, they ARE exactly equivalent. The real challenge is to understand both explanations well enough so that they can be conjoined together as a single explanation. Of course, this is what Einstein did, when he started working towards the General Theory of Relativity.
This is not, unfortunately, how most people react in face of disagreements. The existence of the disagreement is usually chalked up to the ignorance, irrationality, or duplicity on the part of “the other.” That the other side might have a perfectly logistically consistent reason for their explanations eludes most people. Lives of physicists is easier in that, even if they might disagree about the particulars, they do have a common language, mathematics, and the shared assumption that the physical universe obeys mathematical logic, in addition to the absence of personal and emotional stakes about the “rightness” of an explanation in general. Even so, connecting the dots does not come easily. For physicists, the logic of gravity and the logic acceleration were fully laid out and uncontroversial, literally centuries before Einstein. That the two explanations were logically equivalent and indistinguishable, however, did elude physicists a long time nevertheless.
The challenge outside physics, and even sciences, is that disagreement in face of common facts is rarely taken as something to be explained. If one community believes X and the other Y, it is taken as an indication of how “wrong” the other side is since X (or Y) is so self-evident! The universe where data is plentiful but access to which is easily customizable thanks to the Google search engine magic does not help matters. Achieving a consensus even on the basic facts is increasingly difficult, and with such little common data, the universe of potentially competing explanations, each fully consistent within itself, grows exponentially. If a set of competing explanations have to account for, say, both the sun rising in the east and setting in the west, all explanations that imply the sun setting in the north can be discarded. If the only shared “data” consists of the sun rising in the east, there is no reason that a sun setting in the north (or the south) should become necessarily “irrational” within confines of its logic (and shared observations of the reality).
“Universal” rationality, then, is not significant for being “rational” in itself, but for being “universal.” It is significant only so far as everyone in a given community accepts as such. When everyone believes the physical universe obeys rules of mathematics, those who make up the community around this belief can communicate among themselves and build a logical structure building on that common assumption. That the explanations should be consistent with the reality that they all share in observing reinforces this process. Fred Brooks, while discussing authority and project management, said that the important thing is not the manager is right, in factual sense, but that his authority is universally respected so that everyone can get onboard the same boat. (I can’t remember where I read this–this was not in The Mythical Man Month, if I recall correctly, but in some business publication that I read online…could anyone send the link?) In the same vein, however, achieving consensus when there is a disagreement requires understanding the logic behind why the disagreeing parties believe as they do and finding a logic that melds the competing explanations together…not beating over the head of one or the other with just one side’s explanation. This can be hard: cosmological constant hard.