"By the time we've made it, we've had it." - Malcolm Forbes

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Human behavior and psychology is often divided into the rational and the irrational, but one area that is sometimes neglected is the non-rational.

One example is emotion. While emotions can be irrational, and can lead people to do irrational things, in and of themselves they are not necessarily irrational.

If I love someone, this may be emotionally driven and be a non-rational decision, but it is not irrational unless it leads to irrational thoughts or behavior.

Taking a larger view, emotions are a kind of preference. For example, if I prefer chocolate to vanilla ice cream, this has nothing to do with rationality (unless I prefer the taste of vanilla to chocolate, and there is no reason why my preferences would be reversed for ice cream).

We see a similar false dichotomy in morality, where moral and immoral are labels that are often thrown about, but the amoral (what is neither morally good or bad) is often neglected.

What, then, would qualify as irrational behavior or thinking?

One example would be a violation of transitivity. If I prefer chocolate ice cream to vanilla ice cream, and vanilla ice cream to strawberry ice cream, I should prefer chocolate ice cream to strawberry ice cream.

Another would be a violation of means-end rationality. If I want to get to the next town which is 100km away and I have $20, it would be rational for me to take the bus rather than walk (unless I have a lot of time, am stingy etc).

At first glance this restrictive definition of irrationality would seem to discount most of what seems irrational, but you will probably find that a lot of behavior we commonly label irrational can be shown to be such - if you dig deep enough. However, most of us have better things to do (which is why we don't represent arguments in formal logic unless we're in Philosophy Academia).


Addendum:

Or, quoting Hume:

"Reason alone can never be a motive to any action of the will...

Reason is, and ought only to be the slave of the passions, and can never pretend to any other office than to serve and obey them...

A passion can never, in any sense, be called unreasonable, but when founded on a false supposition, or when it chuses means insufficient for the designed end"