Syllogisms are a tool for creating deductive arguments. They are a series of interconnected premises that when chained together lead to a conclusion, and are a specific and powerful way of constructing deductive arguments. The basic form consists of a general statement, known as the major premise, a specific statement known as the minor premise, and a conclusion that is derived from both. The most famous example from antiquity goes as follows:
All men are mortal (major premise)
Socrates is a man (minor premise)
Therefore, Socrates is mortal (conclusion)
You have to be careful when constructing your syllogism that your premise really are connected and do not simply have some words and concepts in common, otherwise you run the risk of falling into a syllogistic trap. Take a look at this argument:
All men are people
Some people are stupid
Therefore, some men are stupid
The conclusion is true: without a doubt, some men are stupid, as anyone who has had the unbridled pleasure of working with one such specimen can attest. The premises, both major and minor, are valid. But take a look at the following example:
All men are people
Some people are women
Therefore, some men are women
The logic is exactly the same as the example before, but the conclusion is obviously ridiculous. This shows that the first example was not really based on logic – it took an accepted conclusion and built a reasonable-sounding syllogism around it. It’s backward reasoning, in a sense. It’s possible for this sort of thinking to manifest itself when we are constructing arguments for things that are less clear-cut, and it should be avoided if you wish to construct sound arguments. It can, of course, still be very persuasive to less perceptive opponents.
There are a number of other syllogistic fallacies to watch out for and keep in mind: a positive conclusion cannot be derived if either of the premises is negative, neither can a negative conclusion be derived if both premises are positive, and no conclusion can be derived at all if both premises are negative.
