.......Keen readers and audiences often ask why Claudius acceded to the throne in Hamlet, Prince of Denmark. Should not the crown have passed to the dead king’s son, Prince Hamlet? 
.......Not necessarily. In Denmark, the setting of the play, an elective monarchy held sway until 1660, when a hereditary monarchy replaced it. Therefore, Shakespeare’s fictional Hamlet, based on a legendary Dane of the Middle Ages, could not claim the crown as a birthright.  
.......In an elective monarchy, court officials–noblemen in high standing–selected the new king by vote. The son of a king was, to be sure, the prime candidate for the royal chair, and usually he won it. But the voting nobles had the right to reject him in favor of another candidate. And that was precisely what happened in fictional Elsinore. The nobles approved the king’s brother, Claudius.  
.......In a hereditary monarchy, the king’s oldest son automatically ascended the throne when his father died.  
.......But of course Danish laws do not explain why the nobles chose Claudius over Hamlet. Shakespeare offers no explanation of their vote. However, in Act V, Scene II, Hamlet refers to the election of Claudius, saying, “He that hath killed my king and whored my mother, / Popped in between the election and my hopes.” These lines appear in a passage in which Hamlet–conversing with his best friend, Horatio–is discussing Claudius’s murder plot against him and his moral right to kill Claudius.  The words “my hopes” may signify that Hamlet expected to succeed his father. In the same scene of the same act, Hamlet–dying from the wound inflicted by Laertes’ poisoned-tip sword–again refers to Denmark election system when he says Fortinbras should be the new king: “But I do prophesy the election lights / On Fortinbras: he has my dying voice.” 
.......That he did not gain accession after the murder of his father could have been due to one or all of the following reasons: (1) Claudius actively campaigned for the kingship, winning votes by promising political favors. (2) Gertrude, eager to remarry and remain queen, campaigned on his behalf. (3) The nobles perceived Hamlet as too young and callow–and perhaps more likely to support the views of the common people instead of their views–and thus denied him succession.  
.......In the tale on which Shakespeare based Hamlet–Amleth, a Latin work by Saxo Grammaticus (1150?-1220?)–Feng (the character after whom Shakespeare modeled Claudius) murders his brother, King Horwendil, out of jealousy. The opening paragraph of Amleth explains the cause of the jealousy: 
 

.......In an 1899 book entitled Interpretation of Dreams, Austrian neurologist Sigmund Freud (1856-1939), the founder of psychoanalysis, introduced the term Oedipus complex. This term describes a psychological stage of development in which a male child desires sexual relations with his mother or a female child desires sexual relations with her father. The child also exhibits hostility toward the parent of the same sex–a boy for the father and a girl for the mother. In normal development, a child outgrows this desire. However, in abnormal development, a child may retain his or her sexual fixation on the parent of the opposite sex.  
.......After Freud coined the term Oedipus complex, Shakespeare scholars noted that Hamlet exhibits the symptoms of this condition in his relationship with his mother, Gertrude, and stepfather-uncle, Claudius. In a soliloquy in Act I, Scene II, Hamlet condemns Claudius as a “satyr” and agonizes over his mother’s hasty marriage to him, saying, “O, most wicked speed, to post / With such dexterity to incestuous sheets!” Ample evidence exists elsewhere in the play to support the Freudian interpretation of Hamlet’s character while buttressing the view that Hamlet is mentally deranged. 
.......In coining his term, Freud drew upon the story of Oedipus in Greek mythology. Here is the story, in brief: 
.......An oracle warns King Laius of Thebes that his wife, Jocasta, will bear a son who will one day kill him. After Jocasta gives birth to a boy, Laius acts to defeat the prophecy. First, he drives a spike through the child's feet, then takes him to Mount Cithaeron and orders a shepherd to kill him. But the shepherd, taking pity on the baby, spares him after tying him to a tree. A peasant finds the baby and gives him to a childless couple–Polybus (also Polybius), King of Corinth, and his wife, Periboea (also Merope). They name the boy Oedipus (meaning swelled foot) and raise him to manhood.  
.......One day, when Oedipus visits the oracle at Delphi, the oracle tells Oedipus that a time will come when he slays his father and marries his mother. Horrified, Oedipus later strikes out from Corinth. He does not want to live anywhere near his beloved parents, Polybus and Periboea, lest a trick of fate cause him to be the instrument of their demise. What he does not know, of course, is that Polybus and Periboea are not his real parents. 
.......On the road to Thebes, which leads away from Corinth, Oedipus encounters his real father Laius, whom he does not recognize, and several attendants. Laius, of course, does not recognize Oedipus either. Oedipus and Laius quarrel over a triviality–who has the right of way. The quarrel leads to violence, and Oedipus kills Laius and four of his attendants.  
.......Outside Thebes, Oedipus encounters the Sphinx, a winged lion with the head of a woman. The grotesque creature has killed many Thebans because they could not answer her riddle: What travels on four feet in the morning, two at midday, and three in evening? Consequently, the city lives in great terror. No one can enter or leave the city.  
.......When Oedipus approaches the Sphinx, the beast poses the riddle. Oedipus, quick of mind, spits back the right answer: man. Here is the explanation: As an infant in the morning of life, a human being crawls on all fours; as an adult in the midday of life, he walks upright on two legs; as an old man in the evening of life, he walks on three legs, including a cane.  
.......Surprised and outraged, the Sphinx kills herself. Jubliant Thebans then offer this newcomer the throne of Thebes. Oedipus accepts it and marries its widowed queen, Jocasta. Jocasta is, of course, the mother of Oedipus, although no one in Thebes becomes aware of this fact until much later. Thus, the oracle's prophecy to Laius and Oedipus is fulfilled. 
.......Hamlet, of course, does not marry his mother. But, according to Freudian interpreters of the play, he does desire her–at least subconsciously. What is more, he solves a riddle of sorts, a homicide case, and kills his father–that is, stepfather. However, unlike Oedipus, Hamlet does not live on to anguish over the past.