Antonio and his friends are walking in a street in Venice when The Merchant of Venice opens and Antonio is lamenting his sadness which "wearies me."(I.i.2) He says that he does not understand why he feels this way and to know would teach him something about himself; he has "much ado to know myself."
Salerio and Solanio offer their thoughts on the reasons for Antonio's melancholy, as his mind is "tossing on the ocean" (7); the most obvious reason being the precarious position of the ships that carry his wealth- his "hopes abroad."(17) Antonio however discounts this as he is thankful that his ships are "not in one bottom trusted"(42), meaning that he is not reliant on only one ship and his "whole estate" is not what makes him sad because he is not reliant on only this year's returns for his fortune.
It seems that Antonio is resigned to "play a part" (78), comparing the world to "a stage." Antonio is content not to seek a reason for his sadness which perhaps stems from the fact that , on this "stage," Antonio's part will be "a sad one." (79)