He did incline to sadness; and ofttimes
Not knowing why."

This uncaused melancholy that distinguishes Romeo, Jaques, Hamlet,
Macbeth, and Vincentio is not more characteristic of the
Hamlet-Shakespeare nature than the way Posthumus behaves when Iachimo
tries to make him believe that he has won the wager. Posthumus is
convinced almost at once; jumps to the conclusion, indeed, with the
heedless rapidity of the naive, sensitive, quick-thinking man who has
cultivated his emotions and thoughts by writing in solitude, and not the
suspicions and distrust of others which are developed in the
market-place. One is reminded of Goethe's famous couplet:

"Es bildet ein Talent sich in der Stille,
Sich ein Charakter in dem Strom der Welt."

Posthumus is all in fitful extremes; not satisfied with believing the
lie, he gives Iachimo Imogen's ring as well, and bursts into a diatribe:

"Let there be no honour
Where there's beauty; truth, where semblance; love,
Where there's another man,"

and so forth. Even Philario, who has no stake in the matter, is
infinitely harder to convince:

"Have patience, sir,
And take your ring again; 'tis not yet won:
It may be probable she lost it."