Sep 15, 2014 | By George Gantz
What does it mean to be “rational”?
This would seem to be an easy question. We all agree human beings can be, and should be, rational. But language and discourse about human thought is notoriously slippery. What being rational means has confounded philosophers for thousands of years. 
There seems to be agreement that being “rational” is about making decisions. The “ratio” part suggests a parsing – a measuring and choosing of options. If we are choosing between options to make a decision, then the process must be directed towards a goal or set of outcomes. What do we hope to accomplish by making the decision? In fact, one common definition of “rational” has been – the making of choices to achieve optimal outcomes.
At the same time, a rational decision is one that is based on facts and information. There are deep disagreements about the admissible range of facts and information (can it include emotions, feelings, hunches, the testimony of others, or revelation and spiritual experience, for example), but there seems to be agreement that the factors behind a rational decision need to be accessible to the conscious mind. Randomness or accident is not “rational”; nor are hidden impulses, which are more appropriately labeled as “biases” that can distort rational decision-making.
Rational decision-making, then, involves a process that takes information, identifies desired outcomes, and yields a decision. That process is most often called “reasoning” – following logical rules and using all available information to determine the choice that optimizes the desirable outcomes. Judging whether someone is rational would then depend on answering these questions:
- Is all available information being utilized?
- Is the desired outcome being achieved (or likely to be achieved)?
- Is the line of reasoning logical?
Leaving aside the first two criteria as topics for another time, let’s consider the third. What does it mean for reasoning to be logical? From an academic standpoint, the answer can get mired in technicalities, but for most people, most of the time, one would have to say that being consistent is the most important feature of logical reasoning, e.g. contradictions must be avoided. It is not logical, or rational, for someone to accept or think two opposite and irreconcilable things at the same time. For example, it is not rational to hold as a goal the idea that you can eat your cake and have it too! It is not rational to presume that you can see what is in front of you if you are walking backwards. It is not rational to hold that something is true and false at the same time. It is not rational to conclude that the apple will not fall if you believe in the law of gravity.
This clarity in the definition of rationality is reassuring, as it seems to provide at least one unassailable basis for judging the quality of our reasoning, or for disputing the rationality of arguments that we exposed to. Most of the time, that is going to be the case. Next week, however, I will talk about some of the problems that we may find in trying to apply this criteria to the most logical of fields of inquiry – mathematics and physics.
In following weeks I will circle back to some of the questions about information and goals. Throughout, I hope to keep the exposition as rational as possible.
 Sometimes, the etymology of a word can help, but in this case many words (according to Wikipedia) including rationality, reason, and logic all derive from the Greek “logos” which could mean “grounds, plea, opinion, expectation, word, speech, account or reason” – and even logos and its companion “lexis” derive from the same verb ”lego” meaning “to count, tell, say, speak.”
 Ironically, this brings us back to another word – reason – that also derives from the Greek “logos”.