Motifs are recurring structures, contrasts, or literary devices that can help to develop and inform the text’s major themes.
The Sacred and the Profane
Volpone, both in his initial speech in Act I and in his seduction speech of Act III, mixes religious language and profane subject matter to a startling poetic effect. In Act I the subject of his worship is money; in Act III it is Celia, or perhaps her body, that inspires prayer-like language. As a foil against this, Celia pleads for a distinction to be restored between the "base" and the "noble," (in other words, between the profane—that which is firmly rooted in our animal natures, and the sacred—that which is divine about humans. Through their respective fates, the play seems to endorse Celia's position, though Jonson invests Volpone's speeches with a great deal of poetic energy and rhetorical ornamentation that make his position attractive and rich, which is again, another source of tension in the play.
Disguise, Deception, and Truth
Jonson creates a complex relationship among disguise, deception, and truth in the play. Disguise sometimes serves simply to conceal, as it does when Peregrine dupes Sir Politic Would-be. But sometimes it reveals inner truths that a person's normal attire may conceal. Volpone, for example, publicly reveals more of his "true self" (his vital, healthy self) when he dresses as Scoto Mantua; and Scoto's speeches seem to be filled with authorial comment from Jonson himself. Furthermore, disguise is seen to exert a certain force and power all of its own; by assuming one, people run the risk of changing their identity, of being unable to escape the disguise. This is certainly the case for Mosca and Volpone in Act V, whose "disguised" identities almost supersede their actual ones.
Read about a similar use of disguise as a motif in William Shakespeare’s Twelfth Night.
Gulling means "making someone into a fool." The question that the play teaches us to ask is: Who is being made a fool by whom? Volpone plays sick to make the legacy-hunters fools, but Mosca plays the "Fool" (the harmless assistant and entertainer) in order to make Volpone into a fool. To make someone else into a fool is both the primary method characters have for asserting power over one another and the primary way Jonson brings across his moral message: the characters in the play who are made into fools—Corbaccio, Corvino, Voltore, Volpone—are the characters whose morality we are supposed to criticize.