I recently had a discussion with a friend of mine about elections, in particular the studies that have shown that a significant number of people vote based upon nothing more than how a politician looks (i.e. photos on their posters). My friend opined that we can actually tell a lot about a person’s trustworthiness by examining their facial features. I objected with the old adage “You can’t judge a book by its cover”, a proverb that has stood the test of time. Does your duck principle not contradict this proverb, and if so can you please explain why the proverb is incorrect?
Let’s look at the duck principle in detail. It says: “if it
looks like a duck,
walks like a duck,
quacks like a duck,
tastes like a duck, it is
very probably a duck”. In other words, we do not just rely on one of the “features”, we walk “around” the subject, expose it many tests, and as long the tests support the hypothesis, we keep on relying on the hypothesis. It does not give us a “100%” assurance (there is no 100% assurance) that the hypothesis was right, but the assurance of “99.9999999…%” is more than sufficient.
The proverb, as is, is quite simplistic compared to the thorough analysis presented above. If you only look at the “cover”, you may very well be mistaken.
Giving another example: if you walk in the desert, and see a “lake-like” phenomenon in the distance, it is reasonable to say: “maybe it is just a mirage, since there are no known lakes around here, and the mirage is a likely occurence in this heat”. If, however, you actually reach the lake, dip into it, swim in it, drink some water from it, then it would be totally irrational to say: “but maybe all that evidence is just a mistake, and there is no lake around here”.
That is the lesson from the duck principle.
