(1) Except as provided in Subsection (4) of this Section, intoxication of the actor is not a defense unless it negatives an element of the offense.

  (2) When recklessness establishes an element of the offense, if the actor, due to self-induced intoxication, is unaware of a risk of which he would have been aware had he been sober, such unawareness is immaterial.

  (3) Intoxication does not, in itself, constitute mental disease within the meaning of Section 4.01.

  (4) Intoxication which (a) is not self-induced or (b) is pathological is an affirmative defense if by reason of such intoxication the actor at the time of his conduct lacks substantial capacity either to appreciate its criminality [wrongfulness] or to conform his conduct to the requirements of law.

  (5) Definitions.  In this Section unless a different meaning plainly is required:

    (a) "intoxication" means a disturbance of mental or physical capacities resulting from the introduction of substances into the body;

    (b) "self-induced intoxication" means intoxication caused by substances which the actor knowingly introduces into his body, the tendency of which to cause intoxication he knows or ought to know, unless he introduces them pursuant to medical advice or under such circumstances as would afford a defense to a charge of crime;

    (c) "pathological intoxication" means intoxication grossly excessive in degree, given the amount of the intoxicant, to which the actor does not know he is susceptible.