At the close of William Shakespeare's play, Much Ado About Nothing, one of the main characters, Benedick, who has throughout the play been opposed to marriage but has been converted by the trickery and machinations of his friends, speaks the conclusion to the play and utters this phrase:
In brief, since I do purpose to marry, I will think nothing to any purpose that the world can say against it; and therefore never flout at me for what I have said against it, for man is a giddy thing, and this is my conclusion. (Much Ado, V.4.103-106)
Man is a giddy thing. A dictionary entry defines the adjective giddy as "having a sensation of whirling and a tendency to fall or stagger; dizzy" (https://languages.oup.com/google-dictionary-en/). What is Shakespeare telling us when he has Benedick describe himself, but not just himself, in these terms? Here, I belie,ve is one of those Meta-Shakespeare quotes where the bard makes a statement that outside the context of the play has as much meaning as it does in context.
For Benedick, his statement is part apology for his changed opinion on the state of marriage. Having stated at previous points in the play that he is "a professed tyrant to their sex" (I.1.160), that marriage is akin to thrusting "thy neck into a yoke" (I.1.191). At another point proclaiming that "I will live a bachelor" (I.1.234). He states that if ever he changes his mind, "let me be vilely painted, and in such great letters as they write 'Here is good horse to hire ... Here you may see Benedick the married man'" (I.1.251-254).
Benedick's position is clear, yet his friend and lord, Don Pedro, proposes to unmask Benedick's false abhorrence of love and to knit his heart to Beatrice, who, while not being as forecful about never marrying anyone, clearly has a complicated relationship with Benedick. It appears that the two were involved at some level previously. Early in the play, Beatrice remarks that "You [Benedick] always end with a Jade's trick. I know you of old" (I.1.138). Later, after the masquerade ball in which Beatrice spoke harshly to Benedick (whether she knew it was him or not is a matter of debate), Don Pedro tells her "you have lost the heart of Signor Benedick." She replies, "Indeed, my lord, he lent it me awhile, and I gave him use for it - a double heart for his single one. Marry, once before he won it of me with false dice; therefore your grace may well say I have lost it" (II.1.261-266).
Don Pedro and others devise a plan to make Benedick and Beatrice believe that the other secretly loves them, thus bringing "Signor Benedick and Lady Beatrice into a mountain of affection th' one with th' other" (II.1.346).
It is this trick played out that changes the heart of Benedick and Beatrice both and gives them leave to love each other. The conclusion to this is that after promising to marry each other, Benedick must explain his previous behavior. Man is a giddy thing. Man is changeable. Man is not surefooted on this earth. Man can change his mind and must when circumstances insist. "When I said I would die a bachelor, I did not think I should live till I were married" (II.3.230), Benedick states when first his mind is altered to new possibilities.
When all else has been accomplished and he and Beatrice are forced to see themselves rightly, Benedick's best explanation for the change in himself is that "Man is a giddy thing."