Themes in Hamlet

In Act I and Act II, Hamlet by William Shakespeare presents themes of revenge and appearance vs reality.  The ghost of the dead King Hamlet is first thought to be only a figment of the guards' imaginations.  However, after further appearances, the ghost is believed to be the true King Hamlet.  During young Hamlet's talk with the ghost of his father, the ghost tells young Hamlet of his murder and tells young Hamlet to seek revenge on Claudius.  Hamlet, however, is very conflicted about what he should do.