She pressures him, using intense psychological pressure, to commit the murder which otherwise he would never have done. Review Act 1 Scene 7. On his own, Macbeth reaches the decision not to kill Duncan. He says, "We shall proceed no further in this business." Lady M then comes in, and by casting aspersions on his masculinity and other emotional tricks, causes him to make a 180 degree turn in the matter of a few lines. Macbeth is the one who uses the daggers, but Lady Macbeth is 100% the guiding mind and will behind the murder.
