How to Think #8: Disamis

Now for our eighth valid syllogism. This one is called Disamis and in symbols it looks like this:

1. Some M's are P's

2. All M's are S's

3. Therefore, some S's are P's

If this one looks familiar there is a very good reason. It is exactly the same as Datisi except we have changed the first word of the first line from "All" to "Some" and the first word of the second line from "Some" to "All." The conclusion remains the same.

In words Disamis might come out like this:

1. Some police officers are criminals

2. All police officers get special treatment from prosecutors

3. Therefore, some people who get special treatment from prosecutors are criminals

Remember, syllogisms are intended to be true without doubt - if they are properly set up. Properly set up means: you use a valid syllogism, the premises are true, and the terms used in the syllogism have the same definition throughout.

So if you are making a syllogistic argument yourself make sure you set it up right. If your opponent makes a syllogistic argument and you disagree with the conclusion here is your line of attack: 1) check to see if the syllogism used is one of the valid forms, 2) check to see if the premises are true, 3) verify that the meanings of the terms used do not change from one line to the next.

If you find a mistake you may be able to refute your opponent's argument. If you can't find a mistake maybe you have found a new truth and will have to change your beliefs to accommodate it.

Copyright © 2016 by Joseph Wayne Gadway

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