The first class that I ever took that was an honest to goodness introduction to logic started with this.
The instructor asked for a show of hands of everyone who was familiar with the show "Star Trek" . I'm pretty sure they all went up.
"Good.Now keep them up if you liked Mr. Spock."
No change as I saw it.
"Now keep your hand up if Mr. Spock was an influence in your taking this class."
Most stayed up, including my own.
"Now, keep your hands up, only if you realize that almost every time Mr. Spock used the word "logical" he used it wrong."
Not a hand remained standing , including my own.
Its true. Almost every time Spock announces that something is logical, he uses the word incorrectly. "Reasonable" just doesn't pack the same dramatic impact.
If something is logical, there can be NO OTHER explanation for the situation. Stating that two plus two equals four (in base ten arithmetic) is very logical. Merely saying that putting a Democrat and a Republican in the same room will result in an argument is reasonable, but not logical. Thy might not even talk politics. Its not even unlikely that they might discover common ground. Maybe they will both agree that a certain senator should go to jail for what he did.
After years of watching the show, I have to agree. He means reasonable when he says logical. In all but a very few cases, his conclusions ignore outcomes that he can't foresee. They are not "logical" in the true sense of the word.
In the real world, almost nothing is.
That last statement should in no means be interpreted as a reason to abandon logic. Hardly. The search for understanding should never be abandoned merely because it is fallible.
Would you stop eating because you once tasted something bad?
That's not reasonable.
Almost every time you hear anyone say that something is logical, they don’t mean that it’s logical –in fact, they mean something almost exactly opposite – that it seems correct based on intuition and common sense.
And common sense tells us that the world is flat.
Okay, bad example. I’ve repeated this little axiom of mine for years, usually to be called out with, “That’s not true, everyone knows the world is round. “
Fair enough, but what do your common senses tell you? Can you see the curvature of the Earth? Do you have any “sense” that the planet is spinning to the east at an incredible speed?
If your honest with yourself you will see that your brain inputs, sight, sound sense of motion, tell you none of this. Using “logic” by most peoples understanding of it, you must deduce that the Earth is flat.
When more information is injected into the equation, then the shape of the Earth can become , well, at least reasonable.
Not every logician accepts this idea that the use of such a word as logical is wrong in this case. Some even suggest that reasonable is to weak a word to be used for the right effect.
There is an episode of Star Trek- The Next Generation that features a race who are just about to make the step that the Vulcans did long ago. That is, control their emotions and use logic. Interestingly, they never refer to their conclusions as logical, bur reasonable. The episode is called “Who Watches the Watchers.