Deductive reasoning is flawed, therefore we should move on.

Consider this common example for an argument of deductive reasoning.

All men are mortal.
Socrates is a man.
Therefore, Socrates is mortal.

We start with a major (general) premise, move to a minor (particular) premise, then draw a conclusion. Not so difficult. But let’s look at the major premise again.

All men are mortal.

I have met many men. Hundreds, perhaps thousands. But to be sure I have not met all men. Every time I go shopping I see someone I have yet to meet. So what am I basing this statement upon, if it is not based upon observations of the men I have met until now. Where do I find the universal truths? I may ask my wife, children, relatives, friends and co-workers too “have you met any man who isn’t mortal?” and usually (there is always one wisecrack who would claim “yes, I have!”) get a favourable answer (does hearsay count?), but I still have not confirmed that all men are indeed mortal.

What I really have done is enumerated (enumerative induction) all of my experiences with men and come to a probable conclusion that this statement ‘all men are mortal’ is a “truth”. What I really should be saying is that “all the men I have met (and heard about) are mortal”. It would not be truthful to make that major premise. It seems, then, all deductive reasoning is based on an assumption from an experience of high-probability without acknowledging itself to be doing so. There is no true deductive reasoning that can be true as such, only probable conclusions.

Now I am not saying probability are not good. I am saying exactly the opposite, that we only ever have most-probable-answers and likely-to-be-true statements to work with. I am saying, deductive reasoning is flawed, therefore, we should move on.

1 thought on “Deductive reasoning is flawed, therefore we should move on.

  1. Pingback: So deductive reasoning does have its uses | the recycling plant

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