How do theories show themselves to be productive? As someone who reads a fair amount of material about linguistics, one often finds situations where writers seek to determine the deep relationships between long-separated languages as a way of showing the family history that has remained hidden over the course of centuries. One of the things that these papers seek to do is to provide evidence of how productive it is to reconstruct the speaking of the past and see how a variety of languages all spring from a common source. To give but one example of this sort of work, it is being demonstrated that almost all the languages of Northern Eurasia spring from only two large families of languages, one family of which contains languages as far removed as Basque, the languages of the Caucasian mountains, the Sino-Tibetan languages of East Asia, and the Na-Dene languages of North America. To think that Basque and Navajo are distant cousin languages who have shared grammar and root words that extend back to a common root is a pretty staggering thought, to be sure, when Basque has long been thought to have been entirely isolated as language.
How do such theories prove themselves to be productive, though? Ideally, if we truly understand something we will be able to gain further insights that we would not have come to without the right pieces sliding into place to show a common picture. One of the elements, for example, that Dene-Caucasian languages share with Afro-Asiatic languages (including, among them, Hebrew and Arabic) is the tendency to connect right and left with bottom and top. A reader of the Bible will be familiar with the way that the left tends to be viewed a typically negative sense–and that if you are on someone’s left side that you are clearly not being preferred. This negative bias against the left is not merely a particular linguistic pattern but extends to a whole host of matters, including such issues as sanitation, where the penalty of thieves by cutting off their right-hand renders them unclean because sanitation and eating are required with the same usually less dominant hand. Thus a knowledge of language and its connections can help someone better understand shared cultural traditions and the implications of language on worldview and behavior. Productivity means that seeing one thing better allows one to see other things better.
There are certainly a great many overarching theories that are not very productive. Such theories attempt to shut off conversation rather than start it, or serve to condemn some people and justify others for doing the same things. We can all think of fashionable theories that attempt to label things in a “just so story” fashion to categorize them as a substitute for understanding them, theories that present themselves to be vitally important in fields of science and the humanities but end up being both morally and intellectually barren. Productivity involves better understanding why things are one way and not another, not merely a retrospective look to say that the same thing can “explain” two entirely contradictory results without understanding pathways, processes, and the like. One of the advantages with, say, linguistics is that changes in linguistics are often like changes in genetics in that there are traces and patterns one can see that can help make sense of how something changes over time. Where such pathways are missing in a stepwise fashion, one cannot properly determine intermediates which must logically exist for the pathway to be a valid one, and which one can then look for the presence of. Productive theories give us a target to aim at, something to look for, in the mass of conceptual space, and not merely an ad hoc and post hoc explanation of that which we already see.