How We Know That Shakespeare Wrote Shakespeare: The ...

3d. Shakespeare bought the Blackfriar's Gatehouse in London in 1613. On the deed dated 10 March 1613, John Hemmyng, gentleman (also spelled Hemming on the same page) acted as trustee for the buyer, "William Shakespeare of Stratford-upon-Avon." This property is disposed of in Shakespeare's will.
So William Shakespeare of Stratford-upon-Avon, gentleman, was the actor who performed in the plays in the company for which William Shakespeare wrote plays. Shakespeare was also a sharer in the syndicate that owned the Globe theater. There were three parties to the agreement: Nicholas Brend, who owned the grounds upon which the Globe was built; Cuthbert and Richard Burbage, who were responsible for half the lease; and five members of the Chamberlain's Men -- William Shakespeare, John Heminges, Augustine Philips, Thomas Pope, and William Kempe -- who were responsible for the other half of the lease. Each of these men had a 1/10 share in the profits. The share dropped to 1/12 when Henry Condell and William Sly joined in 1605-08, and dropped to 1/14 in 1611when Ostler came in.
It may seem like overkill to ask if William Shakespeare the Globe-sharer was the same William Shakespeare of Stratford-upon-Avon, gentleman, since all the sharers were obviously members of the acting company. That he was the same man is easily proven by legal documents.
4b. In a mortgage deed of trust dated 7 October 1601 by Nicholas Brend to John Bodley, John Collet, and Matthew Browne, in which Bodley was given control of the Globe playhouse, the Globe is described as being tenanted by "Richard Burbadge and Willm Shackspeare gent."
4c. In a deed of trust dated 10 October 1601 by Nicholas Brend to John Bodley, legally tightening up the control of Bodley of the Globe, again the theater is described as being tenanted by "Richard Burbage and William Shakspeare gentlemen."
4d. In a deed of sale of John Collet's interest to John Bodley in 1608, the Globe is once more described as being tenanted by "Richard Burbadge and Willm Shakespeare, gent."
(Notice the variation in spelling of Shakespeare's surname between the three documents, all originating in London. For some reason variants of the name seem to be a major point in the minds of some Oxfordians, but such differences are no more significant than similar variants of Richard Burbage's name in the same documents. See The Spelling and Pronunciation of Shakespeare's Name.)
So now we've established that William Shakespeare of Stratford-upon-Avon was an actor in the company that performed the plays of William Shakespeare, and was also a sharer in the theater in which the plays were presented. To anyone with a logical mind, it follows that this William Shakespeare of Stratford-upon-Avon was also the writer of the plays and poems that bear his name. He is the man with the right name, at the right time, and at the right place.
Now, it is true that there exists no play or poem attributed to "William Shakespeare of Stratford-upon-Avon." The name on the works is "William Shakespeare." There also exists no comparable attribution for virtually any of Shakespeare's contemporaries, the only exceptions being some cases where some ambiguity might exist, such as "John Davies of Hereford" and "William Drummond of Hawthornden." But his contemporaries knew who he was, and there was never any doubt in the minds of those who knew him. Following is the most important evidence of this.
5c. In 1615 Edmund Howes published a list of "Our moderne, and present excellent Poets" in John Stow's Annales. He lists the poets "according to their priorities (social rank) as neere I could," with Knights listed first, followed by gentlemen. In the middle of the 27 listed, number 13 is "M. Willi. Shakespeare gentleman."
5f. In the First Folio, John Heminges and Henry Condell said they published the Folio "onely to keepe the memory of so worthy a Friend, & Fellow alive, as was our Shakespeare, by humble offer of his playes." Heminges and Condell had been fellow actors with William Shakespeare in the King's Men for many years, and had been remembered in his will.
5g. In the same volume, Ben Jonson wrote a poem "To the memory of my beloved, The Author Mr. William Shakespeare," in which he says,
Sweet Swan of Avon! what a sight it were
To see thee in our waters yet appeare,
And make those flights upon the bankes of Thames,
That so did take Eliza, and our James!
Here not only does Jonson tie the author to William Shakespeare of Stratford-upon-Avon, but he puts him in James I's court. (See 2c and 2d above.) Oxfordians sometimes attempt to claim that this evidence could apply to Oxford by asserting that Oxford owned an estate on the Avon river. While it's true that one of the many estates Oxford inherited from his father was at Bilton on the Avon river, he sold this estate in 1580 (43 years before Jonson's poem), and there is no evidence that he was ever physically present there.
5h. Also in the Folio, Leonard Digges wrote an elegy "To the Memorie of the deceased Authour Maister W. Shakespeare," in which he refers to "thy Stratford Moniment." Digges presumably knew what he was talking about; he was the stepson of William Shakespeare's friend Thomas Russell, and had close ties to Stratford for most of his life. The only surviving letter by him, written a few years before his death, contains gossip of the "mad relations of Stratford," including Thomas Combe, to whom William Shakespeare had left his ceremonial sword in his will.
5n. Sir Richard Baker, a contemporary of Shakespeare and a friend of John Donne, published Chronicle of the Kings of England in 1643. Sir Richard was an avid fan of the theater, also writing Theatrum Redivium, or the Theatre Vindicated. In the Chronicle, for Elizabeth's reign he notes statesmen, seamen, and soldiers, and literary figures who are mostly theologians with the exception of Sidney. In conclusion he says,
After such men, it might be thought ridiculous to speak of Stage-players; but seeing excellency in the meanest things deserves remembering . . . For writers of Playes, and such as had been Players themselves, William Shakespear and Benjamin Johnson, have specially left their Names recommended to Posterity.