How dose Shakespeare introduce the idea of opposites being the same

Shakespeare often contrasts opposite making them seem like they are but the same option.

Explanation:

He employs this strategy in some of his most famous aphorisms which include 'to be or not to be', and 'fair is foul and foul is fair'.

These statements are comparisons between two diametrically opposite stances which makes an impression that anything is on the table and either of the options will result in the same thing as they are compared directly to each other.

Thus it gives the impression of being the same.