Final answer:
Shakespeare conveys the effect of the past on the present by illustrating Macbeth's desensitization to violence, showing that his previous violent actions have made him numb to horror.
Step-by-step explanation:
Shakespeare develops the universal theme "the impact of the past on the present" in the excerpt from act 5, scene 5 of The Tragedy of Macbeth by showing that Macbeth has become numb to violence. The lines spoken by Macbeth reflect his desensitization to the horrors he has committed. Once susceptible to fear and terror, Macbeth narrates how he has been so steeped in violent deeds that even dire events do not faze him anymore. He indicates that his senses would have previously reacted to dreadful events, but now he is accustomed to horrors due to his past actions, and thus, they have no power to startle him.