Internal evidence.
Shall I set down the rest of the Conjectures which constitute the giant Biography of William Shakespeare? It would strain the Unabridged Dictionary to hold them. He is a brontosaur: nine bones and six hundred barrels of plaster of Paris.
V
"We May Assume"
In the Assuming trade three separate and independent cults are transacting business. Two of these cults are known as the Shakespearites and the Baconians, and I am the other one--the Brontosaurian.
The Shakespearite knows that Shakespeare wrote Shakespeare's Works; the Baconian knows that Francis Bacon wrote them; the Brontosaurian doesn't really know which of them did it, but is quite composedly and contentedly sure that Shakespeare DIDN'T, and strongly suspects that Bacon DID. We all have to do a good deal of assuming, but I am fairly certain that in every case I can call to mind the Baconian assumers have come out ahead of the Shakespearites. Both parties handle the same materials, but the Baconians seem to me to get much more reasonable and rational and persuasive results out of them than is the case with the Shakespearites. The Shakespearite conducts his assuming upon a definite principle, an unchanging and immutable law: which is: 2 and 8 and 7 and 14, added together, make 165. I believe this to be an error. No matter, you cannot get a habit-sodden Shakespearite to cipher-up his materials upon any other basis. With the Baconian it is different. If you place before him the above figures and set him to adding them up, he will never in any case get more than 45 out of them, and in nine cases out of ten he will get just the proper 31.
Let me try to illustrate the two systems in a simple and homely way calculated to bring the idea within the grasp of the ignorant and unintelligent. We will suppose a case: take a lap- bred, house-fed, uneducated, inexperienced kitten; take a rugged old Tom that's scarred from stem to rudder-post with the memorials of strenuous experience, and is so cultured, so educated, so limitlessly erudite that one may say of him "all cat-knowledge is his province"; also, take a mouse. Lock the three up in a holeless, crackless, exitless prison-cell. Wait half an hour, then open the cell, introduce a Shakespearite and a Baconian, and let them cipher and assume. The mouse is missing: the question to be decided is, where is it? You can guess both verdicts beforehand. One verdict will say the kitten contains the mouse; the other will as certainly say the mouse is in the tom-cat.
The Shakespearite will Reason like this--(that is not my word, it is his). He will say the kitten MAY HAVE BEEN attending school when nobody was noticing; therefore WE ARE WARRANTED IN ASSUMING that it did so; also, it COULD HAVE BEEN training in a court-clerk's office when no one was noticing; since that could have happened, WE ARE JUSTIFIED IN ASSUMING that it did happen; it COULD HAVE STUDIED CATOLOGY IN A GARRET when no one was noticing--therefore it DID; it COULD HAVE attended cat-assizes on the shed-roof nights, for recreation, when no one was noticing, and have harvested a knowledge of cat court-forms and cat lawyer- talk in that way: it COULD have done it, therefore without a doubt it DID; it COULD HAVE gone soldiering with a war-tribe when no one was noticing, and learned soldier-wiles and soldier-ways, and what to do with a mouse when opportunity offers; the plain inference, therefore, is that that is what it DID. Since all these manifold things COULD have occurred, we have EVERY RIGHT TO BELIEVE they did occur. These patiently and painstakingly accumulated vast acquirements and competences needed but one thing more--opportunity--to convert themselves into triumphal action. The opportunity came, we have the result; BEYOND SHADOW OF QUESTION the mouse is in the kitten.
It is proper to remark that when we of the three cults plant a "WE THINK WE MAY ASSUME," we expect it, under careful watering and fertilizing and tending, to grow up into a strong and hardy and weather-defying "THERE ISN'T A SHADOW OF A DOUBT" at last-- and it usually happens.