The argument isn't Callow's alone. To be precise, it's Shakespeare scholar Jonathan Bate who's offering it. He's written a lecture on the Bard beautifully disguised as a play to which veteran actor Callow, by his commitment to the proceedings, adds his whole-hearted endorsement.
Not in any way impersonating Shakespeare, Callow arrives in street clothes to run through what's known of the playwright's biographical data. As his peg he takes Jacques' seven-ages-of-man speech in As You Like It. Progressing from the "mewling and puking" infant to the old man "sans teeth, sans eyes, sans taste, sans everything" Callow -- delivering Bates' contentions -- explains how at every stage his brilliant subject had the wherewithal to compose the works others dispute.
For instance, reaching the "whining school-boy years," he chats about young Will attending grammar school where the primary (and only) subject taught was rhetoric. The command he acquired, Callow insists, was sufficient preparation for Shakespeare's incomparable proficiency with language.
The grammar-school period may be the most crucial evidence in the Callow-Bate brief on Shakespeare's behalf, although additional details lend weight. On the other hand, not everything mooted during the two-act, under-two-hours enterprise is persuasive. When the fourth-stage "soldier, full of strange oaths and bearded" arrives, Callow and Bate, unable to provide proof of their boy's military history, conjecture that, like his dramatist pal Ben Jonson, Shakespeare could have fought in one of the constant late 16th-century wars.
Yes, those denying Shakespeare full or partial authorship could poke holes in some of this, but never mind. Whether Being Shakespeare seals the pro-Shakespeare-anti-Edward-de-Vere-and-others debate, it allows Callow, one of the 21st century's foremost character actors, the opportunity to glide fluidly from one Shakespeare excerpt to another. While he doesn't get around to every one of the plays, he lands on most of them.
He plays both Romeo and Juliet in the balcony scene. He's Falstaff denouncing "honor" as having no practical application. He becomes the Midsummer Night's Dream rustics preparing to perform the Pyramus and Thisbe myths for the royals. He's Macbeth learning of his lady's demise. He quotes the sexy "Venus and Adonis" poem and sonnet 18 ("Shall I compare thee to a summer's day?"), noting that both are dedicated to his handsome patron the Duke of Southampton and implying that more may have transpired between the men than meets the eye.
Moving easily and constantly under Tom Cairns' direction and through Cairns' minimal set -- featuring trees in leaf during the first half and leafless for the second -- and with poetic Bruno Poet lighting and imaginative sound by Ben and Max Ringham, Callow ends not by being Shakespeare but by being totally enamored of Shakespeare and relaying that enthusiasm to his rapt audience.