Is denying the antecedent valid or invalid?

Denying the antecedent is an invalid argument form. In other words, it is a formal logical fallacy.

In logic, the term “invalid” describes a type of argument in which the premises do not guarantee the truth of the conclusion, even if all the premises are true. In the fallacy of denying the antecedent, it is possible that the expected outcome could occur without one specific cause being true.

Consider the following example:

  • If an animal is a bird, then it lays eggs.
  • This animal is not a bird.
  • Therefore, it does not lay eggs.

It is clear that this argument is invalid. The animal could be an insect or a reptile or many other animals. The conclusion is not guaranteed by the premises.