One of my seminary professors published a book that is the sum total of every lecture he ever delivered in every class he taught for over 20 years. The first chapter is nothing less than a dictionary. Roy had a penchant for what he called "operating definitions"; he wanted to make clear to others what he meant when he used a word. By calling them "operating" definitions, he was making clear that these were
his ways of using these words in these instances. You could disagree with the definitions; but at least there was the beginning of mutual understanding with the operating definitions in mind.
While the chapter in question is pedantic, as Roy could be on occasion, the practice is a good one. Too often we use words thoughtlessly, assuming words are univocal - having a definition, and therefore an understanding, accessible to all equally. Of course, this is not true of any words, least of all in English, where words, their synonyms and homonyms create a vagueness and mutability of meaning that is breathtaking to consider. As an example (I promise to make this short), consider the word "rose" - it can be a verb (the past tense of rise), a noun with multiple meanings (a flower, a color), or an adjective. Its precise meaning can only be ascertained in any given instance by the context in which it is used. Even then, it can be used as a metaphor rather than have any literal meaning, and therefore might require even deeper interpretation to understand fully.
To me the word I find most frustrating in any kind of serious discussion, and a word rendered meaningless because of overuse, is "rational". What does it mean to be rational? Does it mean emplpoying a certain method of reaching conclusions to questions? Are there rules to this method such that certain criteria need to be met in order to be said to be rational? Are these criteria immutable and universal? Does the employment of such methods, by rendering one rational, make one superior in some way or others to all those who do not use such methods? Does raitonality imply finality, i.e., are decisions and choices and answers to questions arrived at in this way unanswerable precisely because they are rational, and does rationality provide reasons to all questions put?
There is, of course, a school of philosophy that follows Rene Descartes known as rationalism, in which the source of truth is the internal investigation of states of being using logic, assuming of course that logic itself is immutable, and that therefore all persons who so investigate will arrive at similar conclusions. There are few "rationalists" of this stripe any more, with the notable exception of Noam Chomsky who has often cited his discovery of Descartes at an early age to be revelatory, and his subsequent work in linguistics merely an extension of Cartesian methods by other means.
Of course, the questions I pose above concerning the operating definition of "rational" themselves beg certain questions, not the least of which is do I understand what others mean when they use the word. That, however, is precisely my point. That, and its antithesis "irrational" are thrown around so frequently, often as compliments or insults, without any clarity as to how the words are being used, that we are left to conclude either, (a) we are too irrational to understand the word rational; or, (b) the person using the word doesn't really understand what he or she means in using the words in question, and only confuses the issue by tossing them around so freely.
The pair - rational and irrational - are often applied to persons adhering to religious beliefs of one kind or another. It is said that there is no rational explanation to claiming to believe something that is neither demonstrably true or false. Of course, that much is true (it also implies an understanding of rationality as method, but we shall leave that to the side for the nonce). Yet, I would challenge someone to give me a rational explanation (again, implying a method with certain criteria agreed upon by most if not all) for the choices that person has made in his or her life. Of course, as we chase the circle of explanation down this spiral, we should find, if we are honest, that such is impossible. Life is not reducible in this way (and if it is, it isn't life but robotic motion). I am not suggesting that there is not thought in the process of living. Of course there is! I am suggesting that we come to a point in what one modern-day realist philosopher calls "the spiral of reflection" where there are no answers left that satisfy, no reasons that justify, and no generally accessible truths that mark an end to questioning. Human life, in this way, is irrational at its core, because there are irreducible elements that are impervious to rational inquiry.
This is no less true of non-religious than it is of religious life. It is no less true in Christianity than it is Judaism or Islam or Buddhism. It is no less true of those who accept the theories of quantum mechanics (and who can not accept them, relying as I am now on a machine based upon them) with those who refuse to do so (including Albert Einstein and Neils Bohr who refused to accept them; the latter worked out the equations for hydrogen, and it took him two years to do so, and he realized it would take longer than the solar system would exist to work out the equations for the next element, helium. Seeing this as unacceptable, he tossed the theory to one side). Creationists are called irrational, when a better word would be "unscientific", and this in a limited sense that they do not understand the methods of science. Of course, the theory of evolution is scientific, but does that,
ipso facto, make it rational? This, I think is the nub, and would require many volumes of many books to answer.
I find too often that tossing around rational and irrational in discussions mean little beyond the epithetical. We are seeking to compliment, or insult, those with whom we are discussing, as as rationality is one of the hallmarks of Enlightened humanity, and since of course we are all Enlightened now, those who would disagree with us are, by this understanding, irrational. This isn't real argument. It's namecalling disguised as serious argument.
I shy away from using the words at all (except when they can be used in a very constricted sense; the Bush Administration is often irrational in a very precise way - the words and ideas that come from it make no sense no matter how hard one tries to analyze them) precisely because they have become meaningless, even though everyone, it seems, knows what they mean. When we have descended to trying to understand the words we are using in our disagreements, perhaps it is time to find other, better, words to use.