It doesn't really exist. The argument- used by the Oxfordians- that only an aristocrat could have had the experience of the world and depth of culture necessary to produce such work- is pure snobbery. After all, our candidate, Kit Marlowe, was a cobbler's son- and came from even further down the social scale than the glove-making, landowning Shakespeares.
It's just a feeling really.
You look at the records of Shakespeare's life- which are fairly copious- and the picture emerges of an energetic, none too scrupulous businessman. He buys land and property, lends money, does a bit of profiteering, applies for a coat of arms. No reason why a man who leaves this kind of paper trail shouldn't also have written King Lear, Twelfth Night and the Sonnets but somehow it doesn't quite fit. One loves the writer but doesn't entirely like the social-climbing chiseller he seems to have been.
Where did he get his education? Why is there no certain record of him as a writer before he was 29? Isn't it a little odd that so great a genius should have risen without trace?
Our man Kit on the other hand leaves a glittering trail. He goes to university, acquires aristocratic patrons, hangs out with the Luciferian genius Walter Raleigh, travels, does undercover work for the government, writes and publishes plays and poems, translates Ovid- and all before he reaches the age at which Shakespeare emerges from obscurity. Kit at 29 is a man of whom great things might be expected and Shakespeare at the same age is nobody in particular.
And then there's the evidence of the work. Shakespeare is just so Marlovian. His first published work- Venus and Adonis- is heavily influenced by Marlowe's Hero and Leander- which hadn't been published yet, his historical plays plough the furrow that Kit initiated with his Edward II, the style of early Shakespeare- his quirks and quiddities, his vocabulary and all that sort of thing- is practically the same as Kit's. You could say that Shakespeare was imitating his predecessor but you don't expect an imitator to surpass their model- and Shakespeare just keeps on getting better and better.
Where one sticks- a bit- is with the testimony of Shakespeare's contemporaries. Ben Jonson liked and grudgingly admired the man. Hemming and Condell seem to have accepted his authorship. But did any of them stand looking over his shoulder while he wrote? Was there any need for them to be in on the secret? The Shakespeare they knew was a fellow-actor, astute man of the theatre, fun guy to be around. He could have been all these things and still acted as the front for another man's work. Would the deception have been so very hard to maintain? Shakespeare could well have been enough of a writer to effect revisions of Kit's work as it went through the process of production, cutting lines, adding lines, shoehorning in a song or a masque- all that sort of thing. Perhaps he slipped one or two of his own compositions- the Hathaway sonnet for instance- in among Kit's papers- simply because he could. It would explain why there are things in the canon that fall so very far below the general standard.
Case proved? Hardly. Perhaps the document that'll clinch the matter is out there- somewhere- but more probably not. In the end what matters is the work itself and not the name on the title page.
Still one does love a good mystery...