Without consulting a dictionary, I think of a "fool" as someone who, well, should know better. Especially when they hold two sets of beliefs that, if not absolutely opposite, are certainly not in sync.
That is, they believe one thing, but then believe something else that doesn't logically follow. If you believe in A, you shouldn't believe in B. You should know better.
And I don't mean one's a fool for not having the education or experience to spot logical fallacies. By should, I mean there's an ethical responsibility to know better when one does have the capacity to recognize the fallacy.
One example of the fool: someone who says, "Only stupid people play the lottery," but then says, "Your vote can make a difference." If the odds of winning the lottery make it not worth the dollar to play, how is spending a chunk out of one's day to vote worth anything, when the odds of that vote making a difference are astronomical? Can one be that bad at math?
It's more sensible to say, your vote can make a difference, in the same way you can win the lottery.
This week, however, brings to mind another kind of fool: those who believe that JFK was murdered by the CIA (or even think it's possible), who then go on to express hope and faith in other Presidential candidates, and in our system of government as a whole.
If one believes the CIA could do this and get away with it, one must concede the CIA is, or is part of, a Secret Government that's in control of the visible, "democratically-elected" government.
And even if one doesn't believe in the CIA theory, but only believes it's possible, that itself is proof there's no reason to have faith in "our system of government." To think it's possible that a Secret Government exists, is to express sufficient doubt to make "faith" in our government a waste of energy.
To think of the CIA theory as possible or probable, and to STILL have faith in the system, is to believe that at some point, post-JFK, this Secret Government voluntarily give up its power.
Instead of living with such delusions, it's better to give up faith in our "government" altogether.