Rules on Civil Procedure
Section 5. Defenses. - Defenses may either be negative or affirmative.
(a) A negative defense is the specific denial of the material fact or facts alleged in the pleading of the claimant essential to his cause or causes of action.
(b) An affirmative defense is an allegation of a new matter which, while hypothetically admitting the material allegations in the pleading of the claimant, would nevertheless prevent or bar recovery by him. The affirmative defenses include fraud, statute of limitations, release, payment, illegality, statute of frauds, estoppel, former recovery, discharge in bankruptcy, and any other matter by way of confession and avoidance. (5a)