How to Think #2: BARBARA, Cont.

Let's cover a couple more points about syllogisms using Barbara before we move on to the next one.

First, here is another example of Barbara:

1. All politicians tell lies
2. All presidential candidates are politicians
3. Therefore, all presidential candidates tell lies.

Now look at this one:

1. All college professors are intelligent
2. Doctor Smith is a college professor
3. Therefore, Doctor Smith is intelligent.

This second example looks different from the first because the second line is about one person rather than "all" the members of a group. But that's OK. Whether the second line is about a group or an individual, the syllogism is still Barbara and still valid.

As we have already stressed, if the premises of a valid syllogism are true, then the conclusion MUST be true. But if the premises are false that does not prove the conclusion is false. It just means we don't know.

One more thing to watch out for. Sometimes people get confused when a conclusion is true and assume that the syllogism must prove the conclusion.

But consider this:

1. Everything Joe owns is a car
2. A Toyota Camry is one of the things Joe owns.
3. Therefore a Toyota Camry is a car.

Now we may believe that it is true that a Toyota Camry is a car but this syllogism does not prove it. The syllogism is an example of Barbara so we know it is valid. But the first premise is not true so the syllogism is not sound and does not prove its conclusion. We may know through some other means that a Toyota Camry is a car but this particular argument is a failure.

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Copyright © 2016 by Joseph Wayne Gadway

How to Think #1: BARBARA

Deductive arguments are one of the five major types of arguments. The other types of arguments are inductive, abductive, based on testimony, or based on authority. The three-line arguments called syllogisms are one of the major types of deduction. In this series of posts I will describe, and give examples of, the valid syllogisms.

I will also link to some great books you can read to learn more about how to think!

There is a valid syllogism called Barbara! It is called Barbara for theoretical reasons we will get to later. For now, this is how Barbara looks in symbols:

1. All M's are P's
2. All S's are M's
3. Therefore, All S's are P's.

This is a "valid" syllogism, meaning that, if the premises are true, then the conclusion MUST be true.

Replace the symbols with words and you could get something like this:

1. All mammals have four-chambered hearts
2. All squirrels are mammals
3. Therefore: All squirrels have four-chambered hearts.

These premises are true so this syllogism is both "valid" and "sound."

One more example of Barbara:

1. All Democrats are Liberals
2. All the people in Massachusetts are Democrats
3. Therefore, all the people in Massachusetts are Liberals.

Now this is Barbara so we know the syllogism is valid, but in this case both of the premises are false so the argument is not "sound." The conclusion might still be true, but it is not supported by the premises because they are NOT true.

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[If you want to support "Anything Smart" just click on book links like the one below and the other ones throughout this post to buy your books. "Anything Smart" will receive a commission. Thanks!]

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Copyright © 2016 by Joseph Wayne Gadway