In Macbeth what are Banquo's external or internal forces?

Banquo, in Macbeth, is a character
similar in some aspects to Macbeth.  While Banquo believes in the prophecies, much like
Macbeth, he does not take action to fulfill them.

Banquo
sees that Macbeth's prophecy has come true.  He, therefore, trusts in the fact that his
will as well (his sons will gain the throne).  Fortunately for Banquo, he does not take
any actions to insure the prophecy.  He believes that if they are meant to come true,
they will on their own. Internally, Banquo must face the fact, internally, regarding the
person that Macbeth has become because of the prophecy. He, not willing to become
something else, trusts in fate.

Externally, Banquo is
Macbeth's antagonist (in the form of the ghost).  Banquo, for Macbeth, represents the
good. Banquo must make the decision to act virtiously. He chooses, in the face of
Macbeth's murderous actions, to remain vigilant and noble. The external forces brought
upon him are Macbeth's actions and the prophecy of the witches. Banquo must face these
challenges while remaining a good person.