Affirming the Consequent with Jehovah's Witnesses

It is possible to write an entire book on logical fallacies and use nothing but Jehovah’s Witness arguments for examples.

Everybody uses logic when they reason. They just don’t use it formally. They don’t spell out their premises and their conclusions explicitly. The arguments are more implicit. To really think carefully about the arguments people make, you have to be able to reformulate their arguments explicitly. Doing so can be very revealing. Here’s an example:

Jehovah’s Witnesses will point to 2 Timothy 3:12, which says that “everyone who wants to live a godly life in Christ Jesus will be persecuted.” Then they will point out how badly they are persecuted. (Usually, voicing your disagreements with them is enough for them to call it persecution.) That’s it. They’ll stop right there. But what’s the point they’re trying to make? You see, this is an example of how people don’t spell out their arguments. They just hint around at it, and you have to take the hint. But the point is usually obvious. They’re pointing to 2 Timothy 3:12 and the fact that they are persecuted in order to show that they are the true Christians.

When you spell this argument out explicitly, you can see that it commits one of the most basic formal logical fallacies there is. It’s one of the first that you’ll learn about if you ever take a logic class. Here’s the argument put formally.

1. If you want to live a godly life in Christ Jesus, then you will be persecuted.
2. Jehovah’s Witnesses are persecuted.
3. Therefore, Jehovah’s Witnesses want to live a godly life in Christ Jesus.

This argument commits the fallacy of affirming the consequent. It is logically invalid.

A valid modus ponens looks like this:

1. If P then Q
2. P
3. Therefore, Q.

But the Jehovah’s Witness argument affirms the consequent instead of the antecedent, and their argument takes this form:

1. If P then Q
2. Q
3. Therefore, P