The pathetic fallacy is defined as...
...the treatment of inanimate objects as if they had human feelings, thought, or sensations.
Though the word "pathetic" is used that has negative connotations for us, here it is used to indicate "empathy" or "capable of feeling," and is not derrogatory. My sense is that "pathetic fallacy" personifies an inanimate object with human characteristics, but goes one step beyond to provide it with some emotional quality.
The atmosphere created in William Shakespeare's Macbeth, in Act Two, scene one, is found in Macbeth's "dagger speech," prior to the murder of Duncan.
When Macbeth looks at the dagger, he not only personifies it, but gives it the capacity of some emotion:
Art thou not, fatal vision, sensible
To feeling as to sight? (44-45)
The fact that Macbeth speaks to the dagger personifies it; then he wonders if it is "sensible" to feeling and sight. In other words, is the "floating" dagger "capable of being perceived by the senses?" "Fatal vision" personifies the dagger has being capable of causing death, whereas only a human hand holding it could bring about death.
Because Macbeth cannot be sure of what he is seeing, he states:
Mine eyes are made the fools o’ the other senses... (52)
In this case, eyes cannot be fools, and the other senses cannot make the eyes to "feel" foolish.
Next, Macbeth makes note of dreams:
...wicked dreams abuse [deceive]
The curtain'd sleep... (58-59)
Here the dreams are personified as able to deceive (a human characteristic), but Shakespeare goes on to refer to the dreams as able to be wicked, capable of some emotion or, in this case, the character of a human rather than just an action.
These uses of pathetic fallacy create a dark and chilling atmosphere, with images that speak strongly of death—especially in light of Macbeth's task at hand: to murder Duncan, his King and his friend.