Leaving aside the variable strictures of legal procedure in and out of any court or differing systems of law, the basic consideration of evidence by the jurist or the historian is essentially the same.

Evidence is something, including testimony, documents, and tangible objects, that tends to prove or disprove the existence of an alleged fact (e.g., Stratford Will was Shakespeare).

In a trial, the two adversarial sides will offer their allegations of fact in complaint and answer, accompanied by any evidence they have to prove or disprove their allegations. Sometimes there are no disputes about the facts, but when there are, the jury (if there is one) or the judge sits as the "fact-finder" who given a standard (e.g., beyond a reasonable doubt, preponderance of the evidence, etc.) assesses how much the evidence offered by both parties proves which sides allegations of fact are "true," which is to say logically inferred to be the most, well, evident.

A classic definition by 19th century legal scholar published in the Harvard Law Review is helpful further: “Evidence is any matter of fact which is furnished to a legal tribunal, otherwise than by reasoning or a reference to what is noticed without proof, as the basis of inference in ascertaining some other matter of fact.” 

In other words, claims on the basis of fact-less reasoning (e.g., we don't know how but Stratford Will must have somehow acquired advanced if imperfect legal knowledge because the plays are replete with law) and claims based on a reference noted without factual proof (Stratford Will might have acquired rudimentary legal concepts at the King's New School assuming he attended)... are not evidence.

"Conspiracy theories have two main characteristics: they explain everything by reference to a single factor, and they can never be disproven."

To which does this definition more apply -- the case for Oxford or the case for Stratford Will?

The case for the latter essentially is every variant spelling and pronunciation of Stratford Will's last name assumes that every variant spelling and pronunciation of the author Shakespeare's name demonstrates the two are the same person. That is the single factor. Assuming it, his authorship can never be disproven.

The case for Oxford does not rely on any single factor.

SB replied: The instances I've mentioned of Jonson's life are a matter of historical record, and Donaldson's biography very well regarded. 

Mark Haslett wrote: That is not a reasonable definition of "evidence."

SB replied: It's a perfectly fair one.

Mark Haslett wrote: Hall's claims are evidence that contemporaries of Shakespeare believed the name was a pen name to such a degree that more than one put their belief in print so others could see it.

SB replied: Hall's claims can at best be taken as evidence of his doubt that Will of Stratford wrote Venus & Adonis. They wouldn't be accepted as undeniable proof by any court.

Mark Haslett wrote: Furthermore, the fact that, although Hall's work was popular, no one ever contradicted Hall's claims is evidence that his claims were not controversial to his colleagues.

SB replied: Or perhaps they just didn't believe him and didn't consider his claims worth repeating.

Mark Haslett wrote: But you are a Shakespeare Phd and not a historian. This does not seem to oblige you to the same depth of intellectual curiosity about such matters.

SB replied: Yes, having a PhD in Shakespeare (well, his plays) obviously means I'm not qualified to talk about him, or them.

Mark Haslett wrote: This can account for why every historian and Supreme Court justice who looks seriously at the Shakespeare authorship question 

SB replied: I can't speak for the United States, but here in the UK, Alternative Authorship theories are pretty much classed by academics alongside doubts about the moon landing and belief in the Loch Ness Monster.

Mark Haslett wrote: Steven keeps presenting the case as an elliptical leap from some known associations among business partners in the theater and an assumption that there cannot be 2 men in the same business at the same time with the same name.

SB replied: In 1603, William Shakespeare is named alongside Heminges and Condell in the royal patent confirming the creation of The King's Men.

In 1616, William Shakespeare (or Shakespere, or Shakespear - as is conventional for the time, the surname is spelt in a variety of ways) dies in Stratford-Upon-Avon, naming Heminges and Condell in his will.

In 1623, the First Folio is published. In it, Heminges and Condell named Shakespeare as the author of the plays contained within.

What is the Oxfordian rebuttal to this? That the Heminges and Condell (and Richard Burbage, also named in the royal patent of 1603) named in the will of William Shakespeare aren't the same Heminges and Condell listed in the royal patent and the First Folio? It's another monumental coincidence?

>>

Mark Haslett wrote: That is not a reasonable definition of "evidence."

SB replied: It's a perfectly fair one.

>>

That's a conversation-killer, Steven. It would hardly be an irrelevant tangent for you, if you disagree with Mark about what defines evidence, to instead of automatically responding "yes" to his "no" actually engaged in a carefully reasoned argument about why you disagree with him. If you and Mark cannot find common ground on what evidence is, why bother arguing anything?

To which does this definition more apply -- the case for Oxford or the case for Stratford Will?

SB replied: Oxford, easily.

To believe that he was the author, we have to believe that he concealed his identity as a playwright while being acclaimed as one, worked with a series of collaborators - Marlowe, Middleton, Beaumont, Fletcher - who either never suspected the truth or chose not to reveal it, or were afraid to do so, wrote plays which betray a lack of historical and geographical understanding utterly inconsistent with the education and background a member of the nobility would typically receive and also wrote them years or even decades before they were performed and when they're usually dated, somehow anticipating how theatre was going to develop and anticipating historical events like the accession of James VI and the Gunpowder Plot, or at roughly the same they were recorded as being first performed, largely adhering to the generally, if not universally, accepted chronology, but also meaning that he kept producing work after dying in 1604, all the time refusing to take any action against this upstart provincial whose very unusual surname is the same as the pseudonym he's using despite having no need to do so and who is unfairly being praised as the author of the work that Oxford has actually written, or co-written.

Or William Shakespeare from Stratford- Upon-Avon wrote, or co-wrote, the plays bearing his name. 

:)

SB replied:  What's to argue? The definition of evidence I've provided -  "a body of facts or information indicating whether a belief is true" - seems to me to be perfectly sufficient. I'm sure there are other definitions, and I'm happy for them to be provided.