Which of the following is not true of unsound arguments?

All unsound arguments commit a formal fallacy.
If a deductive argument commits a fallacy, then it is an unsound argument.
Any argument that commits a formal fallacy is an unsound argument.
If a deductive argument has false premises, then it is an unsound argument.

Unsound arguments, are when the argument is valid but at least one of the premises is false, an invalid argument, or (if they’ve really messed up) the argument is invalid and at least one of the premises is false. To get knowledge of the conclusion, the argument needs to be sound.

All unsound arguments commit a formal fallacy.

The correct answer is: "If a deductive argument commits a fallacy, then it is an unsound argument." This statement is not true of unsound arguments.

To determine which of the statements is not true of unsound arguments, let's examine each statement individually:

1. "All unsound arguments commit a formal fallacy."
To evaluate this statement, we first need to understand what unsound arguments and formal fallacies are. An unsound argument is an argument that is either invalid or has at least one false premise. On the other hand, a formal fallacy is a flaw in the logical structure of an argument. It means that the argument does not follow the rules of deductive logic.

Given these definitions, we can conclude that not all unsound arguments commit a formal fallacy. It is possible for an unsound argument to have a valid logical structure but contain at least one false premise. Therefore, the statement is not universally true.

2. "If a deductive argument commits a fallacy, then it is an unsound argument."
This statement accurately reflects the definition of an unsound argument. If a deductive argument commits a fallacy, it means that there is an error in the logical structure of the argument. Consequently, the argument is no longer valid, making it unsound. Therefore, this statement is true.

3. "Any argument that commits a formal fallacy is an unsound argument."
This statement is also true. As defined earlier, a formal fallacy indicates a flaw in the logical structure of an argument. If an argument commits a formal fallacy, its structure is invalid, which automatically renders it unsound.

4. "If a deductive argument has false premises, then it is an unsound argument."
According to the definition of unsound arguments, this statement is accurate. If a deductive argument contains at least one false premise, the truth of the premises cannot guarantee the truth of the conclusion. Consequently, such an argument would be unsound.

Based on our analysis, statement 1, "All unsound arguments commit a formal fallacy" is the one that is not true of unsound arguments.