"No more that thane of Cawdor shall deceive / Our bosom interest: go pronounce his present death, / And with his former title greet Macbeth."
What is the significance of this quote from Macbeth in terms of theme, making connections, etc.?
This quotation is one of King Duncan's lines in Act 1. The captain has returned from battle and has reported that the Thane of Cawdor is in fact a traitor because he gave important information to the Norwegian army. Duncan wants him immediately removed from his position and plans to give the title to Macbeth because Macbeth fought valiantly in the name of Scotland. This quotation is important because it establishes Duncan's character traits--Duncan believes in loyalty to Scotland and he believes that Macbeth would do anything to protect the country. The irony of Macbeth's killing Duncan begins here--Duncan ultimately trusts Macbeth and believes that he deserves to be honored, but Macbeth is motivated by personal greed and intends to do whatever he can to further his position.
The quote represents King Duncan's words when the king realizes that the Thane of Cawdor has worked in collusion with the Norwegians in order to help them defeat Duncan. The king strips the thane of his position at once, and, as a result, Macbeth is promoted for his valiance and loyalty to the king:
What he hath lost noble Macbeth hath won.
The quote demonstrates that the king has a very high opinion of Macbeth and values qualities such as valor, loyalty, and true friendship. He wants to honor those who exhibit such qualities, and we see him placing his hopes into Macbeth, believing Macbeth is one of his biggest supporters.
The tragic tone starts to permeate the play once we realize that Macbeth is ready to abuse the trust which king Duncan has put in him for the sake of fulling his own evil ambitions. Although he has every reason to protect the king, Macbeth dares to create disorder by plotting to kill him so that he can become the king himself. He murders Duncan, but that very action will ultimately result in Macbeth's own downfall.