(A) A person knows, or acts knowingly or with knowledge of:
(1) The nature or attendant circumstances of his conduct, described by the section defining the offense, when he is consciously aware that his conduct is of such nature or that such circumstances exist. Knowledge of a material fact includes awareness of the substantial probability that such fact exists.
(2) The result of his conduct, described by the section defining the offense, when he is consciously aware that such result is practically certain to be caused by his conduct.
(B) Conduct performed knowingly or with knowledge is performed willfully, within the meaning of a statute using the latter term, unless the section clearly requires another meaning.
(ILCS Ch. 720, Act 5, § 4-5)