In Macbeth, Lennox may be said to be extremely careful in his speech. Why is he so cautious in what he says? What, if anything, could be...

Lennox was introduced in Act II, Scene 3, when he came with Macduff to wake King Duncan and was standing outside the King's chamber trying to make conversation with Macbeth when Macduff discovered the murdered body. At that time Lennox's dialogue characterized him as very young and naive. He was obviously starting out in his career as a courtier and soldier. Then he dropped out of sight until Act III, Scene 6. Shakespeare uses this character very adroitly to show that a lot of time has passed and that there have been a lot of changes in the country under Macbeth's rule. Lennox has become much older and wiser. He has learned to talk ironically, often saying the exact opposite of what he means. The effect is to show the audience that Macbeth is a villain and has become a tyrant. Macbeth rules by fear, not unlike Hitler in Nazi Germany, or Stalin in Soviet Russia, or Robespierre during the French Revolution. Macbeth has spies everywhere, even acting as servants in private households. One might estimate that something like eight or ten years have passed since Macbeth murdered Duncan and was crowned king. The whole country lives in fear. Everyone has to watch what he says, because if he says the wrong thing and it gets back to Macbeth, he could disappear and never be heard from again.

In Act IV, Scene 3, Ross, who is newly arrived in England, will describe conditions in Scotland in more explicit language to both Macduff and Malcolm: 

Alas, poor country,
Almost afraid to know itself! It cannot
Be call'd our mother, but our grave. Where nothing,
But who knows nothing, is once seen to smile;
Where sighs and groans and shrieks that rend the air,
Are made, not mark'd; where violent sorrow seems
A modern ecstasy. The dead man's knell
Is there scarce ask'd for who, and good men's lives
Expire before the flowers in their caps,
Dying or ere they sicken.

Lennox is only saying, in closely guarded language, what everyone now knows. Macbeth murdered Duncan. He had Banquo murdered by agents and tried to have Fleance murdered along with his father. Macbeth would love to get his hands on Malcolm, Donalbain, and Fleance so that he could have them executed. He would accuse Malcolm and Donalbain of bribing Duncan's attendants to kill him in his sleep, and he is quite capable of accusing Fleance of being responsible for his father Banquo's murder.

Shakespeare frequently uses scenes like III.6 to convey information to his audience. The most important news comes from the unidentified Lord when Lennox concludes his monologue and asks:

I hear Macduff lives in disgrace. Sir, can you tell
Where he bestows himself?

The Lord informs Lennox, and the audience, that Macduff is living at the English court with Duncan's son Malcolm, who fled there after his father's assassination. Both are trying to persuade King Edward to help them overthrow the tyrant Macbeth and install Malcolm as King of Scotland. This foreshadows the climax, in which an army of 10,000 English soldiers and Scottish defectors with Malcolm and Macduff in their vanguard invade Macbeth's realm and Macduff kills Macbeth in hand-to-hand combat.