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Cogency

An argument is cogent if its inductive, strong and all of its premises are true. A cogent argument is by definition non-deductive, which means that the premises are intended to establish probable (but not conclusive) support for the conclusion, therefore a cogent argument is only probable. Cogency can be considered the analog in inductive logic to solidity in deductive logic.

Examples

We must always remenber that we cant asume the conclusion will be true, just probable.

• Example 1:

Having a bag filled with 100 marbles, without looking inside we extract 95, all them red coloured. Therefore, is probable that the next marble will be red too.

The truth of the premises would certainly make the conclusion true. Accordingly, this argument is strong. If the premises are true, the argument is cogent.

• Example 2:

1. Most of the substances that are carcinogenic for mice are carcinogenic for humans.

2. Benzene is carcinogenic for mice.

_______________________________________________

3. Therefore, benzene is carcinogenic for humans.

As we said, probably it can be true, but we can´t be sure.

• Example 3:

1. Duch people are tall

2. Daniel is dutch

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3. Daniel is tall.

Not cogent arguments

Now that we know what a cogent argument looks like, lets see what is not a cogent argument.

1. Most of the students at CSUS are women.

2. Elizabeth is a student at CSUS.

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3. Therefore, Elizabeth is a woman.

This example is cogent, notice how the next one is not.

1. Most of the students at CSUS are women.

2. Elizabeth is a woman.

______________________________________________

3. Therefore, Elizabeth is a student at CSUS.

While both premises are true, in no way can they lead to that conclusion.

Probable

There is no fixed standart about how probable must an argument be to be called so. Just as one can speak of different degrees of probability, one can consider different degrees of cogency. The cogency degree depends on the probability degree. On the previous example, the fact that she extracted the 96th ball and it was red would make the conclusion even more probable, and consequently strengthen the argument.

A good argument

To consider an argument a good argument it must be solid or cogent. However, these are necesary qualities but not sufficient. In example, a circular argument can be solid, but certainly is not a good argument. In the same way, a cogent argument could be begging the question. It is different from a valid argument, in which true permises lead to a guaranteed truth of the conclusion.

Further reading

Short and on point video about cogency

A Concise Introduction to Logic, 11th Ed. (Patrick Hurley, 2012)

Category:Logic