What a gentleman! What a brilliant stroke of genius!
The weary army near the end of their campaign, promised beer, wine and new underwear as a reward, see this last bridge beyond which lies their goal - Madrid. Tapas, bullfights, and all business closed between noon and three in the afternoon - no exceptions.
A squad of soldiers is sent to the head of the bridge. They're really excited and just about to run across this bridge when they suddenly hear, "Now, you don't want to do that."
"No, I believe we do," answered their leader, a short white bearded sergeant, with annoyance.
"What are you doing?"
"We're crossing this bridge with twenty-five thousand foot, six thousand horse and seventy-six cannon, head three miles to the outskirts of the capital city, defeat any resistance we meet, march straight to the palace and hang our banners from it and claim this land for Prussia!"
"How do you know the bridge isn't there?"
"Of course it's there!"
"No, I'm asking if you know if it ISN'T there?"
"Now isn't that asking the same exact thing!?!" The men point their bayoneted muskets at the gentleman, clearly aggravated and wanting anything but a single wise guy bothering them.
The gentleman takes a long puff on his pipe, cool and collected, and stands up from where he is seated under an apple tree.
"My dear pupils, I beg your pardon, but they are not a tautology - 'the same thing' - but rather a converse in logic. I was asking rather if you knew that bridge WASN'T there."
"Why wouldn't it be there? It's right there in plain sight!"
"Well, your shadow is in plain sight but it isn't anything of tangible substance."
"Oh, bleedin' hell." One gruff sergeant picks up a rock and throws it onto the bridge where it skips along before sliding over the edge and into the ravine below. "Now how can that not be tangible substance? And who do you think you are sittin' under that apple tree, Sir Isaac Newton?"
The gentleman looked stung. "I? I sir? I am not Sir Isaac Newton! I am Don Señor Gonzalo Nuñez Villacamba Diego Rosaflores Riveras GarrrrrrrrrrrOCHO el Valiente Brillante!"
All the soldiers give one another bizarre looks, turning their tall mitre caps, their muskets casually tilting along with the movement. After a pause, the sergeant asked, "What?"
The gentleman straightens his posture with his back tucked in and chest out in proud Spaniard fashion, proudly proclaiming, "Don Señor Gonzalo Nuñez Villacamba Diego Rosaflores Riveras GarrrrrrrrrrrOCHO el Valiente Brillante!"
"Okay, okay, Mr. Don Senior Bongalo jibber jabber smackety." The gentleman looked a bit perturbed but didn't say anything at that butchering of his name. "What do we call you for short?"
The gentleman slouched and sighed. "Gonzalo Garrocho will do."
"Alright, Mr. Gonzalo Garrocho, explain to us, just ONE MORE TIME, why that bridge there isn't perfectly just dandy wonderful for us to cross this river. We want to get there before the siesta hits, you know!"
"For important matters of learning and science, a single curious mind can outdo a thousand strong arms. Mis compadres, do you agree that what you see, MAY exist?"
"Aye, yes..."
"And do you agree that what you do not see, MAY NOT exist?"
"Well, sure..."
"Then it logically remains and follows that what you see, MAY NOT exist."
"Well blimey, we've crossed nigh two hundred bleedin' bridges on our way here an' not a single ONE has failed to exist while our feet crossed over it!"
Another soldier: "Well, Hans, back at Montélimar there was that one wooden creaker watched over by that toothless toll keeper, an' great fat Kurtz went straight through to the icy river below -"
"SHUT IT!!!" The sergeant points his musket again at the gentleman. "Now I'm losin' my patience, we all are losing our patience - an' if I don't get this 'advance' squad across to the other side within the - MINUTE - the general will lose his patience too and there's no time or pleasantries or dainty tea parties to be spent, delaying our crossin' THIS HERE BRIDGE!"
The gentleman sighs and looks away, twisting his long moustache. "Mil tragedias. Your doom."
The sergeant just about turns as red as the apple the gentleman is absently holding in his hand. "ARRRGGGHHH! If my wife Frieda or the Devil himself doesn't hang it all!!! WHY CAN'T WE CROSS THIS BRIDGE!"
"Matter is all but mind."
"Well, hear this - MATTER IS MATTER and you can put a sock in your mind and a dead skunk too!"
The gentleman seems calm as ever and unperturbed, and all the soldiers are either sitting now, with their caps off, some dozing off already in the lazy Spanish summer heat, starting to stack their muskets in tripods but mostly lay them on the ground where they are. The irony! "Isn't it a principle of knowledge that until any thought is perceived, it may not exist?"
The sergeant is so enraged he can't say anything now but merely stand there with this shoulders hunched up and his nose, beard and fists quivering with silenced fury.
The gentleman doesn't heed the sergeant's fury and takes the silence as agreement. He continues to take out a pocketknife and peel and cut the apple and continues, "It is an analogous theory that anything that you don't see, may not exist either."
The sergeant finally burst out. "HA! See! That's a theory! Just a theory! It isn't true!"
"¡Mi amigo! So is gravity of your dear Isaac Newton just a theory, that holds you to the ground where you are so you don't go floating off in another direction or swept away by the wind. So is cardiopulmonary circulation such that when you breathe, your blood is aerated such that you don't keel over and pass out. So is the planetary rotation that gives us day so that our world doesn't permanently freeze into ice and night so that we don't scorch into a barren wasteland."
"So why can't we cross this here bridge?"
"I repeat again the simple factual possibility that it may not exist."
"So what if it doesn't!"
The gentleman walks over to the edge of the ravine. "That's a pretty far drop of about eighty-five feet. Not even twenty-five thousand foot, six thousand horse and seventy-six cannon can cross this gorge. Unless, of course, you purport to LAUNCH all twenty-five thousand horse, six thousand horse, and six thousand horse-men to the other side by use of the cannon, seventy-six at a time. That is a whole other calculation of how quickly the battery of artillerymen can load, aim, and fire all the men, equine, and paraphernalia as a calculation of Work over Time. And then that doesn't even take into account the possible force strains it places on the body to accelerate it so fast."
"Well, how about we accembrerate YOUR body over to the other side, and then we finally CROSS THE BRIDGE IN PEACE!"
"Dear me, but that still leaves us at square one. The bridge may not exist."
"WHY IN THE WORLD NOT?"
"We have spent the last ten minutes discussing this already but I understand it may take more rumination and explanation to cinch the matter. Because, in a very crude explanation, all the matter in the universe, as it is, has been, and perceivably will be, has a nigh one-hundred percent PROBABILITY that it is there."
"Why, that's bloody well fantastic then!"
"But the catch is that there is a very, very, infinitesimal - but NON-ZERO - chance that it will suddenly dematerialize, without warning, and very most likely with no recourse."
"Now that's something I've never seen 'appening in me whole young life," the grey-haired-and-bearded short sergeant said.
"But just because the lightning doesn't come out of the sky to shock you, or the stray volcano doesn't erupt under you, doesn't mean that it can't happen."
"But it won't!"
"You need not jump to overarching conclusions, and you surely must not mean what you say."
"I do!"
"So you mean to say that something that CAN happen, will NOT happen?"
"No, that is not what I said!"
"But you just did."
The sergeant is about to go over the top and throttle the taller gentleman (who knows how???), while the bored soldiers are absently watching him and probably expecting him to do that or probably club him over the head with his canteen, when the general comes galloping up and his horse scrapes to a halt. All the soldiers are alarmed at his sudden arrival and try to immediately come back to order, tucking in their uniforms, brushing off dust, putting their caps back on (the wrong way) and picking up their rifles and clumsily saluting while do so. "Now I demand to know what is the holdup here? You should have been over the San Tomás bridge already with your squad, checked the other side which we already see is safe and abandoned, and sent back the clearance for the rest of the army to cross! This is quite routine, Sergeant!"
"I was about to, when this here gen-til-man started lecturin' us on why it may not exactly be safe to cross!"
The general snaps the brim of his hat and throws his arm down to his side in anger and dissatisfaction, dismounts, and stomps over to the still-bemused gentleman. "What exactly do you purport to be doing here, knave!"
"Why, I was just musing the vagaries and perplexities of organ music and how it relates to the resonances of different weather patterns, in this tranquil spot, when these men came across me in the middle of my peaceful work."
"Organ music?" The general's expression instantly brightens and he grins excitedly. "My uncle was a most accomplished organist back at Lützen! I swear, if I didn't take up the commission, I just very well may have become a church musician!"
"Do you speak of Johann Sebastian Bach? A veritable pioneer in the art of organ playing and episcopal music."
"No, but I know of whom you speak of! My uncle studied under him. Say, it is a hot day. Why don't you come over to my pavilion and have some cool kirsch?... no, it is too rude and lowly of me to offer."
"No, by no means, good sir. I find your account quite fascinating!"
"And I find your own knowledge no less intriguing! Oh, please do come." And before anyone can object, the general whistles, and one of his bodyguard brings an extra horse - the sergeant's horse actually - and the gentleman mounts it and they gallop back off: Garrocho: "Have you ever tracked the rotation of pendular movement during the day?" The general: "No, I haven't! Just how it does so is a veritable mystery..."
The sergeant, now also flabbergasted, is just left standing there gaping at what happened.
The third soldier who spoke up before asked, "So, Hans, do you really think the bridge is there after all?"
The sergeant's moustache quivers a moment, and then again even more, and finally right before where the stone bridge began on their side, he drops face down on the ground pounding and kicking the ground screaming, "IS! THERE! ISN'T! THERE! IS! THERE! ISN'T! THERE!"
(Sorry for the long corny humor.

I did refer to the Schrödinger electron and some weird idea in quantum physics, but Schrödinger wasn't yet alive in the 18th century so I related some other Medieval metaphysics or whatnot instead. Oh, that Don Señor Gonzalo Nuñez Villacamba Diego Rosaflores Riveras GarrrrrrrrrrrOCHO el Valiente Brillante!)