# Question about validity of Modus Tollens vs. Denying the Antecedent

## Can denying the antecedent be valid?

Denying the antecedent is not a valid form of reasoning. An argument is valid if its premises can be used to logically deduce its conclusion. However, denying the antecedent is a fallacy or a mistake in reasoning, so an argument that used it would be one where the premises cannot be used to deduce the conclusion.

## Why is denying the antecedent an invalid argument form?

Like modus ponens, modus tollens is a valid argument form because the truth of the premises guarantees the truth of the conclusion; however, like affirming the consequent, denying the antecedent is an invalid argument form because the truth of the premises does not guarantee the truth of the conclusion.

## Are all modus tollens arguments valid?

Therefore, I will get an A. An argument form is valid if, no matter what statements are substituted for the premises statement variables, if the premises are all true, then the conclusion is also true.

Modus Ponens Modus Tollens
Therefore, I will wear my sunglasses. Therefore, it is not bright and sunny today.

## Is modus tollens valid or invalid?

Modus tollens is a valid argument form. Because the form is deductive and has two premises and a conclusion, modus tollens is an example of a syllogism. (A syllogism is any deductive argument with two premises and a conclusion.) The Latin phrase ‘modus tollens’, translated literally, means ‘mode of denying’.

## Is modus tollens denying the antecedent?

Like modus ponens, modus tollens is a valid argument form because the truth of the premises guarantees the truth of the conclusion; however, like affirming the consequent, denying the antecedent is an invalid argument form because the truth of the premises does not guarantee the truth of the conclusion.

## What is the difference between affirming the consequent and denying the antecedent?

Affirming the Consequent: “If A is true, then B is true. B is true. Therefore, A is true.” Denying the Antecedent: “If A is true, then B is true.

## Why is this fallacy called denying the antecedent?

Description: It is a fallacy in formal logic where in a standard if/then premise, the antecedent (what comes after the “if”) is made not true, then it is concluded that the consequent (what comes after the “then”) is not true.

## Can modus tollens have false premises and a true conclusion?

FALSE. A valid argument can have false premises; and it can have a false conclusion. But if a valid argument has all true premises, then it must have a true conclusion.

## Is denying a disjunct valid?

To deny a disjunct and affirm the other disjunct as a conclusion is a validating form of argument in propositional logic which is called “disjunctive syllogism”―see the Similar Validating Forms, above.

## Is denying the consequent valid?

The opposite statement, denying the consequent, is a valid form of argument. Denying the consequent can be considered a form of abductive reasoning.

## Is Fallacy of the Inverse valid?

Common patterns of reasoning (Fallacy of the Inverse)

will be an invalid argument. This is a common form of invalid reasoning known as Fallacy of the Inverse.

## What makes an argument valid?

An argument is valid if the premises and conclusion are related to each other in the right way so that if the premises were true, then the conclusion would have to be true as well.

## Can valid arguments have false conclusions?

FALSE: A valid argument must have a true conclusion only if all of the premises are true. So it is possible for a valid argument to have a false conclusion as long as at least one premise is false.

## Do all valid arguments have true conclusions?

All valid arguments have all true premises and true conclusions. All sound arguments are valid arguments. If an argument is valid, then it must have at least one true premise.

## Why is validity truth preserving?

Validity as (Material!) Truth-Preservation in Virtue of Form

ABSTRACT: According to a standard story, part of what we have in mind when we say that an argument is valid is that it is necessarily truth preserving: if the premises are true, the conclusion must also be true.

## Which of the following patterns is the invalid argument form known as affirming the consequent?

The invalid argument form known as affirming the consequent has this pattern: If p, then q. q. Therefore, p.. The invalid argument form known as denying the antecedent has this pattern: If p, then q.

## Do all invalid arguments preserve falsity?

But neither does an invalid argument guarantee that falsity in the premises will be preserved in the conclusion. In other words, an invalid argument may have one or more false premises and a true conclusion (consider J and L).