§ 3018. Responsive pleadings. (a) Denials. A party shall deny those
statements known or believed by him to be untrue. He shall specify those
statements as to the truth of which he lacks knowledge or information
sufficient to form a belief and this shall have the effect of a denial.
All other statements of a pleading are deemed admitted, except that
where no responsive pleading is permitted they are deemed denied or
avoided.

(b) Affirmative defenses. A party shall plead all matters which if not
pleaded would be likely to take the adverse party by surprise or would
raise issues of fact not appearing on the face of a prior pleading such
as arbitration and award, collateral estoppel, culpable conduct claimed
in diminution of damages as set forth in article fourteen-A, discharge
in bankruptcy, facts showing illegality either by statute or common law,
fraud, infancy or other disability of the party defending, payment,
release, res judicata, statute of frauds, or statute of limitation. The
application of this subdivision shall not be confined to the instances
enumerated.