Answer:
Note here how the regularity of the iambic rhythm and the enjambment of the lines through "heat-oppressèd brain" work together to quicken the tempo from the heavier phrasing and punctuation in the beginning. In this context, fatal doesn't quite denote "deadly" (although that makes a ripe double entendre) than it does "foreboding mischief and death; ominous" or, arguably, "instrumental to destiny." (Fatal derives from Middle French via the Latin fatum, meaning prophecy or doom—literally, what has been spoken.) Sensible here denotes "perceptible, tangible" when viewed in its relation to the end of Macbeth's question.
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To feeling as to sight? Or art thou but
Feeling in this line denotes "the sense of touch." The answer to Macbeth's rhetorical question is, of course, "no" since he's already tried to clutch the dagger and failed. However, the potent combination of language and Macbeth addressing this dagger as if it were a character onstage forces the audience to visualize that dagger hovering in front of him.
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A dagger of the mind, a false creation,
"Dagger of the mind" can read in two ways. First, there's the literal contrast of tangible reality and Macbeth's imagination. Second, you have metaphor of Macbeth's guilt—and doubt—manifesting itself as a vision as he waits upon the signal from his wife. False in this context plays upon a number of meanings. While the primary reading is "unreal," shades of "deceitful, inconstant; not to be trusted" are equally applicable. Keep in mind that Macbeth is asking three questions in the first seven lines, which reflects the struggle that Macbeth is still undergoing in coming to terms with his intended crime.
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Proceeding from the heat-oppressèd brain?
Macbeth acknowledges that the dagger that has appeared could be a trick of his imagination (in this case, perhaps induced by a fever). Proceeding is used in its meaning of "issuing or emanating," while heat-oppressèd is Shakespeare's poetic way of saying "fevered." The usage of fever is another simple but amazingly effective piece of imagery in this speech. Fever is a symptom of a disease in its literal meaning. As a metaphor, fever denotes a state of heightened or intense emotion or activity. The disease, in this instance, is ambition.
Explanation:
https://www.bardweb.net/content/readings/macbeth/lines.html
Hope this helps.
