And so I left my companion, not knowing what he had in mind. As I made my way back to the Englischer Hof, I passed a man going hurriedly the other way. The first time I had lived through these terrible events I did not know him, but this time I recognized him for Professor Moriarty: tall, clad all in black, his forehead bulging out, his lean form outlined sharply against the green backdrop of the vegetation. I let the simulation pass, waited fifteen minutes as Holmes had asked, then returned to the falls.
Upon my arrival, I saw Holmes’s Alpine stock leaning against a rock. The black soil of the path to the torrent was constantly re-moistened by the spray from the roiling falls. In the soil I could see two sets of footprints leading down the path to the cascade, and none returning. It was precisely the same terrible sight that greeted me all those years ago.
“Welcome back, Watson!”
I wheeled around. Holmes stood leaning against a tree, grinning widely.
“Holmes!” I exclaimed. “How did you manage to get away from the falls without leaving footprints?”
“Recall, my dear Watson, that except for the flesh-and-blood you and me, all this is but a simulation. I simply asked Mycroft to prevent my feet from leaving tracks.” He demonstrated this by walking back and forth. No impression was left by his shoes, and no vegetation was trampled down by his passage. “And, of course, I asked him to freeze Moriarty, as earlier he had frozen the Swiss lad, before he and I could become locked in mortal combat.”
“Fascinating,” said I.
“Indeed. Now, consider the spectacle before you. What do you see?”
“Just what I saw that horrid day on which I had thought you had died: two sets of tracks leading to the falls, and none returning.”
Holmes’s crow of “Precisely!” rivaled the roar of the falls. “One set of tracks you knew to be my own, and the others you took to be that of the black-clad Englishman — the very Napoleon of crime!”
“Yes.”
“Having seen these two sets approaching the falls, and none returning, you then rushed to the very brink of the falls and found — what?”
“Signs of a struggle at the lip of the precipice leading to the great torrent itself.”
“And what did you conclude from this?”
“That you and Moriarty had plunged to your deaths, locked in mortal combat.”
“Exactly so, Watson! The very same conclusion I myself would have drawn based on those observations!”
“Thankfully, though, I turned out to be incorrect.”
“Did you, now?”
“Why, yes. Your presence here attests to that.”
“Perhaps,” said Holmes. “But I think otherwise. Consider, Watson! You were on the scene, you saw what happened, and for three years — three years, man! — you believed me to be dead. We had been friends and colleagues for a decade at that point. Would the Holmes you knew have let you mourn him for so long without getting word to you? Surely you must know that I trust you at least as much as I do my brother Mycroft, whom I later told you was the only one I had made had privy to the secret that I still lived.”
“Well,” I said, “since you bring it up, I was slightly hurt by that. But you explained your reasons to me when you returned.”
“It is a comfort to me, Watson, that your ill-feelings were assuaged. But I wonder, perchance, if it was more you than I who assuaged them.”
“Eh?”
“You had seen clear evidence of my death, and had faithfully if floridly recorded the same in the chronicle you so appropriately dubbed `The Final Problem.’”
“Yes, indeed. Those were the hardest words I had ever written.”
“And what was the reaction of your readers once this account was published in the Strand ?”
I shook my head, recalling. “It was completely unexpected,” said I. “I had anticipated a few polite notes from strangers mourning your passing, since the stories of your exploits had been so warmly received in the past. But what I got instead was mostly anger and outrage — people demanding to hear further adventures of yours.”
“Which of course you believed to be impossible, seeing as how I was dead.”
“Exactly. The whole thing left a rather bad taste, I must say. Seemed very peculiar behavior.”
“But doubtless it died down quickly,” said Holmes.
“You know full well it did not. I have told you before that the onslaught of letters, as well as personal exhortations wherever I would travel, continued unabated for years. In fact, I was virtually at the point of going back and writing up one of your lesser cases I had previously ignored as being of no general interest simply to get the demands to cease, when, much to my surprise and delight—”
“Much to your surprise and delight, after an absence of three years less a month, I turned up in your consulting rooms, disguised, if I recall correctly, as a shabby book collector. And soon you had fresh adventures to chronicle, beginning with that case of the infamous Colonel Sebastian Moran and his victim, the Honorable Ronald Adair.”
“Yes,” said I. “Wondrous it was.”
“But Watson, let us consider the facts surrounding my apparent death at the falls of Reichenbach on May 4th, 1891. You, the observer on the scene, saw the evidence, and, as you wrote in `The Final Problem,’ many experts scoured the lip of the falls and came to precisely the same conclusion you had — that Moriarty and I had plunged to our deaths.”
“But that conclusion turned out to be wrong.”
Holmes beamed intently. “No, my Good Watson, it turned out to be unacceptable — unacceptable to your faithful readers. And that is where all the problems stem from. Remember Schrödinger’s cat in the sealed box? Moriarty and I at the falls present a very similar scenario: he and I went down the path into the cul-de-sac, our footprints leaving impressions in the soft earth. There were only two possible outcomes at that point: either I would exit alive, or I would not. There was no way out, except to take that same path back away from the falls. Until someone came and looked to see whether I had re-emerged from the path, the outcome was unresolved. I was both alive and dead — a collection of possibilities. But when you arrived, those possibilities had to collapse into a single reality. You saw that there were no footprints returning from the falls — meaning that Moriarty and I had struggled until at last we had both plunged over the edge into the icy torrent. It was your act of seeing the results that forced the possibilities to be resolved. In a very real sense, my good, dear friend, you killed me.”
My heart was pounding in my chest. “I tell you, Holmes, nothing would have made me more happy than to have seen you alive!”
“I do not doubt that, Watson — but you had to see one thing or the other. You could not see both. And, having seen what you saw, you reported your findings: first to the Swiss police, and then to the reporter for the Journal de Geneve, and lastly in your full account in the pages of the Strand.”
I nodded.
“But here is the part that was not considered by Schrödinger when he devised the thought experiment of the cat in the box. Suppose you open the box and find the cat dead, and later you tell your neighbor about the dead cat — and your neighbor refuses to believe you when you say that the cat is dead. What happens if you go and look in the box a second time?”
“Well, the cat is surely still dead.”
“Perhaps. But what if thousands — nay, millions! — refuse to believe the account of the original observer? What if they deny the evidence? What then, Watson?”
“I — I do not know.”
“Through the sheer stubbornness of their will, they reshape reality, Watson! Truth is replaced with fiction! They will the cat back to life. More than that, they attempt to believe that the cat never died in the first place!”
“And so?”
“And so the world, which should have one concrete reality, is rendered unresolved, uncertain, adrift. As the first observer on the scene at Reichenbach, your interpretation should take precedence. But the stubbornness of the human race is legendary, Watson, and through that sheer cussedness, that refusal to believe what they have been plainly told, the world gets plunged back into being a wavefront of unresolved possibilities. We exist in flux — to this day, the whole world exists in flux — because of the conflict between the observation you really made at Reichenbach, and the observation the world wishes you had made.”
“But this is all too fantastic, Holmes!”
“Eliminate the impossible, Watson, and whatever remains, however improbable, must be the truth. Which brings me now to the question we were engaged by this avatar of Mycroft to solve: this paradox of Fermi. Where are the alien beings?”
“And you say you have solved that?”