In A Midsummer Night's Dream, Shakespeare points out that both love and art suspend reality, making illusion the current reality. Both can suspend reality because both are based on emotions, which tend to be irrational, rather than concrete, objective, thought. Shakespeare uses the Athenian lovers to show how love can suspend reality and Theseus's rational opinions about art to show that art can do likewise.
We especially see how feelings of love can suspend reality when we learn that Demetrius actually does not have any rational reason for having rejected Helena. Helena points out that all over Athens, she is recognized to be just as beautiful as Hermia, as we see in her line, "Through Athens I am thought as fair as she" (I.i.232). Helena further points out that love is not based on any objective reality, such as beauty, it is rather a figment of the imagination, as we see in her lines, "Love looks not with the eyes, but with the mind; / And therefore is wing'd Cupid painted blind" (239-240). Therefore, since love is an irrational emotion, feelings of love are based on illusion rather than reality. Furthermore, love suspends reality making reality be perceived as something that it is not.
Shakespeare uses Theseus to point out that the same is true for all art. Theseus is portrayed as one of the play's only rationally-minded characters. He is so rationally minded that, against Egeus's wishes, he grants Demetrius permission to marry Helena, and Hermia permission to marry Lysander. Hence, using Theseus to point out the irrationality of art is very significant to Shakespeare's overall argument in the play. Theseus declares that both "lovers and madmen have such seething brains" (V.i.5). He further states that "[t]he lunatic, the lover, and the poet, / Are of imagination all compact," meaning that all three turn reality into something that it is not (8-9). The lunatic imagines he or she sees "more devils than vast hell can hold"; the lover sees "Helen [of Troy]'s beauty" in very unlikely faces; and, the poet creates shapes out of nothing (10-18). Hence, Theseus is pointing out that the artist, such as the poet, uses imagination to see things that are not really there, thereby suspending reality. The artist, such as the poet, can do this just like the lover because art stems from emotions, which are irrational.