“You have forgotten the Catholics.”

“No, sir, the King has forgotten ’em. Much has changed since you were locked up. First he locked up the Anglican bishops for refusing to preach toleration of Catholics and Dissenters.”

“I know that much-I was a free man at the time,” Daniel said.

“But the whole country was like to rise up in rebellion, Catholic churches were being put to the torch just for sport, and so he let ’em go, just to quiet things down.”

“But that is very different from forgetting the Catholics, sergeant.”

“Ah but since- since you’ve been immured here-why, the King has begun to fall apart.”

“So far I’ve learned nothing remarkable, sergeant, other than that there is a sergeant in the King’s service who actually knows how to use the word ‘immured.’ “

“You see, no one believes his son is really his son-that’s what has him resting so uneasy.”

“What on earth do you mean?”

“Why, the story’s gotten out that the Queen was never pregnant at all-just parading around with pillows stuffed under her dress-and that the so-called Prince is just a common babe snatched from an orphanage somewhere, and smuggled into the birth-chamber inside a warming-pan.”

Daniel contemplated this, dumbfounded. “I saw the baby emerge from the Queen’s vagina with my own eyes,” he said.

“Hold on to that memory, Professor, for it may keep you alive. No one in England thinks the child is anything but a base smuggled-in changeling. And so the King is retreating on every front now. Consequently the Anglicans no longer fear him, while the Papists cry that he has abandoned the only true faith.”

Daniel pondered. “The King wanted Cambridge to grant a degree to a Benedictine monk named Father Francis, who was viewed, around Cambridge, as a sort of stalking-horse for the Pope of Rome,” he said. “Any news of him?”

“The King tried to insinuate Jesuits and such-like everywhere, ” said the sergeant, “but has withdrawn a good many of ’em in the last fortnight. I’d wager Cambridge can stand down, for the King’s power is ebbing-ebbing halfway to France.”

Daniel now went silent for a while. Finally the sergeant resumed speaking, in a lower, more sociable tone: “I am not learned, but I’ve been to many plays, which is where I picked up words like ‘immured,’ and it oftimes happens-especially in your newer plays-that a player will forget his next line, and you’ll hear a spear-carrier or lutenist muttering ‘im a prompt. And in that spirit, I’ll now supply you with your next line, sir: something like ‘My word, these are disastrous tidings, my King, a true friend to all Nonconformists, is in trouble, what shall become of us, how can I be of service to his Majesty?’”

Daniel said nothing. The sergeant seemed to have become provoked, and could not now contain himself from prowling and pacing around the room, as if Daniel were a specimen about whom more could be learned by peering at it from diverse angles. “On the other hand, perhaps you are not a run-of-the-mill Nonconformist, for you are in the Tower, sir.”

“As are you, sergeant.”

“I have a key.”

“Poh! Do you have permission to leave?”

This shut him up for a while. “Our commander is John Churchill,” he said finally, trying a new tack. “The King no longer entirely trusts him.”

“I was wondering when the King would begin to doubt Churchill’s loyalty.”

“He needs us close, as we are his best men-yet not so close as the Horse Guards, hard by Whitehall Palace, within musket-shot of his apartments.”

“And so you have been moved to the Tower for safe-keeping.”

“You’ve got mail,” said the sergeant, and flung a letter onto the table in front of Daniel. It bore the address: grubendol london.

It was from Leibniz.

“It is for you, isn’t it? Don’t bother denying it, I can see it from the look on your face,” the sergeant continued. “We had a devil of a time working out who it was supposed to be given to.”

“It is intended for whichever officer of the Royal Society is currently charged with handling foreign correspondence,” Daniel said indignantly, “and at the moment, that is my honor.”

“You’re the one, aren’t you? You’re the one who conveyed certain letters to William of Orange.”

“There is no incentive for me to supply an answer to that question,” said Daniel after a brief interval of being too appalled to speak.

“Answer this then: do you have friends named Bob Carver and Dick Gripp?”

“Never heard of them.”

“That’s funny, for we have come upon a page of written instructions, left with the warder, saying that you’re to be allowed no visitors at all, except for Bob Carver and Dick Gripp, who may show up at the oddest hours.”

“I do not know them,” Daniel insisted, “and I beg you not to let them into this chamber under any circumstances.”

“That’s begging a lot, Professor, for the instructions are written out in my lord Jeffreys’s own hand, and signed by the same.”

“Then you must know as well as I do that Bob Carver and Dick Gripp are just murderers.”

“What I know is that my lord Jeffreys is Lord Chancellor, and to disobey his command is an act of rebellion.”

“Then I ask you to rebel.”

“You first,” said the sergeant.

Hanover, August 1688

Dear Daniel,

I haven’t the faintest idea where you are, so I will send this to good old GRUBENDOL and pray that it finds you in good health.

Soon I depart on a long journey to Italy, where I expect to gather evidence that will sweep away any remaining cobwebs of doubt that may cling to Sophie’s family tree. You must think me a fool to devote so much effort to genealogy, but be patient and you’ll see there are good reasons for it. I’ll pass through Vienna along the way, and, God willing, obtain an audience with the Emperor and tell him of my plans for the Universal Library (the silver-mining project in the Harz has failed-not because there was anything wrong with my inventions, but because the miners feared that they would be thrown out of work, and resisted me in every imaginable way-and so if the Library is to be funded, it will not be from silver mines, but from the coffers of some great Prince).

There is danger in any journey and so I wanted to write down some things and send them to you before leaving Hanover. These are fresh ideas-green apples that would give a stomach-ache to any erudite person who consumed them. On my journey I shall have many hours to recast them in phrasings more pious (to placate the Jesuits), pompous (to impress the scholastics), or simple (to flatter the salons), but I trust you will forgive me for writing in a way that is informal and plain-spoken. If I should meet with some misfortune along the way, perhaps you or some future Fellow of the Royal Society may pick up the thread where I’ve dropped it.

Looking about us we can easily perceive diverse Truths, viz. that the sky is blue, the moon round, that humans walk on two legs and dogs on four, and so on. Some of those truths are brute and geometrickal in nature, there is no imaginable way to avoid them, for example that the shortest distance between any two points is a straight line. Until Descartes, everyone supposed that such truths were few in number, and that Euclid and the other ancients had found almost all of them. But when Descartes began his project, we all got into the habit of mapping things into a space that could be described by numbers. We now cross two of Descartes’ number-lines at right angles to define a coordinate plane, to which we have given the name Cartesian coordinates, and this conceit appears to be catching on, for one can hardly step into a lecture-room anywhere without seeing some professor drawing a great + on the slate. At any rate, when we all got into the habit of describing the size and position and speed of everything in the world using numbers, lines, curves, and other constructions that are familiar, to erudite men, from Euclid, I say, then it became a sort of vogue to try to explain all of the truths in the universe by geometry. I myself can remember the very moment that I was seduced by this way of thinking: I was fourteen years old, and was wandering around in the Rosenthal outside of Leipzig, ostensibly to smell the blooms but really to prosecute a sort of internal debate in my own mind, between the old ways of the Scholastics and the Mechanical Philosophy of Descartes. As you know I decided in favor of the latter! And I have not ceased to study mathematics since.