"Great Dunsinane he strongly fortifies // some say he's mad, others that lesser hate him."
I will go through Macbeth's soliloquies and chart his character as it changes. A soliloquy is a speech made only to oneself, or even only thought.
Macbeth's first soliloquy is in Act I, Scene III. Two of the things that the witches predicted have come true and Macbeth is contemplating how the third will come true. He thinks about killing Duncan, but he knows that these are only thoughts and he dismisses it and decides to leave it to chance and time.
"Present Fears // Are less than horrible imagining."
"Whose (Duncan) murder is yet but fantastical."
We can see that his mind is confused and distorted, because of what has happened and what may happen, and here we see the first signs of ambition, even though it is dismissed.
"My thought . // Shakes so my single state of man."
The second soliloquy is in Act I, Scene IV, when the Thane of Cawdor has been killed. Duncan describes him as a man on whom I built an absolute trust'. This parallels Macbeth, who he trusts, when he betrays him. Duncan pronounces his son as the prince of Cumberland and the heir to the throne. This throws Macbeth's mind into even more confusion, as this is a step which (he) must o'er-leap. He also, in the soliloquy, knows that his thoughts are evil, and he does not want good to see them.
"Stars, hide your fires, // Let not light see my black and deep desires."
In the third soliloquy Macbeth is still contemplating how he obtains the throne, but now he knows that murder is the only way, yet he fears judgement' and damnation. We see here that Macbeth has a conscience, and his mind cannot take the simple fact. He begins bringing up lots of excuses as to why he should not do it, but inevitably his ambition gets the better of him.
"He's here in double trust: // his kinsman and his subject, // then as his host, // who should against his murder shut the door, // Not bear the knife myself."
"I have no spur // to prick the sides of my intent, but only // Vaulting ambition."
On the battle field, where emotions are not needed and a hindrance, Macbeth would know what to do. However, this conflict is going on inside his mind, and he is not fully competent in this field.
By the time of the forth soliloquy, he has changed character completely. He is no longer the fearless, brave and courageous soldier he once was. This is the famous floating dagger' soliloquy, possibly the most important. This is probably his mind getting him ready for such and act, psyching himself up, by modern terms. In the first half of the soliloquy he is talking about the dagger.
"Art thou not, fatal vision, sensible // to feeling as to sight."
"A dagger a false creation. // from the heat-oppresséd brain."
Then Macbeth starts talking about how the dagger appears to lead him to Duncan's room, when it reappears with bloodstains on it.
"Thou marshall'st me the way that I was going."
The second half of the soliloquy Macbeth is talk about the devious act of murder itself, and what it causes and what it means. He talk about all things that are bad and evil.
"Witchcraft Pale Hecate (witch goddess) Murder Wolf Tarquin."
He compares these things to a present horror'. He gives murder a name, and he personifies it, and makes it an object.
All of these soliloquies show how ambitious he is, but also how ary of what will happen to him. He is a soldier, and this kind of killing...