Final answer:
Lady Macbeth uses indirect language and metaphor to obscure the heinousness of the planned murder and to psychologically distance herself and Macbeth from the act of regicide. This manipulation also serves to coax Macbeth into committing the crime by minimizing its moral gravity.
Step-by-step explanation:
Lady Macbeth uses indirect words when talking about killing Duncan to Macbeth as a way to manipulate and encourage him to commit the regicide. She chooses her words carefully to avoid direct confrontation with the moral weight of murder and instead focuses on the outcomes they desire. Her language is suffused with metaphor and euphemism, which both conceals the gravity of their intent and acts as a psychological device to distance themselves from the act.
For instance, when Lady Macbeth says, "What cannot you and I perform upon The unguarded Duncan?", she is not directly saying 'let's murder Duncan'; instead, she is suggesting an action without naming it, which can be interpreted as a strategic attempt to ease Macbeth into the idea of regicide. Similarly, terms like 'great quell' are used instead of 'murder' to mitigate the impact of their planned crime.