Damned plot bunnies. They burn my biscuits, they really do...

Disclaimer: They're not mine - if they were, I'd do something about Castiel's coat. And Sam's hair. And Dean's mouth. And dietary habits. And collars. FIX YOUR DAMNED COLLAR RIGHT NOW!

Title: The Scientific Method

Summary: Castiel is fascinated by humans' endless capacity to want to know about, well, everything. He decides to explore the intellectual satisfaction of the human way of finding things out. Provided it doesn't involve putting cats in boxes.

Rating: T. What can I say? Dean talks. (Would cheerfully gag him, but there are other websites for, ahem, that that sort of fanfic.)

Blame: The blame for this story lies with whichever one of the regular Denizens of the Jimiverse shooed the plot bunny in my direction. I KNOW it's you lot, so don't all try to hide behind each other, or else - no more G.D.N. (Gratuitous Dean Nudity) or G.S.N. (Gratuitous Sam Nudity) for you! Holy crap, am I turning into the Nudity Nazi?...

I reserve the right to write Castiel as nerdy, earnest, clueless, generator of confusion. Haven't seen S6 yet, but don't like the sound of Robo-Cas one bit.

Of the saving graces of humanity, Castiel thought that it was their endless curiosity about, well, everything that helped make them so… loveable. If he had been asked, he would have named the species first identified in Dordogne in France as Homo percuriosus – the highly inquisitive ape.

He never ceased to be amazed at the capacity of his Father's human children to want to understand, to know. He had observed this trait on countless occasions: the four-year-old who saw a chemistry demonstration on the television, then ran into the kitchen and started mixing things from the pantry with bicarbonate soda, and wondered why vinegar made an interesting mess, water made a less vigorous mess but almond essence just made a smelly mess. (A peek into her future showed that she would major in biological sciences, with chemistry as a minor, and spend her career researching treatments for a particularly insidious type of toxic chemical.) The retired physics professor who made a hobby of constructing a mathematical model of the electron states of iron, because it was always her favourite element for its peculiarly stable nature. (She never finished it, of course, but it kept her happy and intellectually engaged into her mid-nineties; an ex-student who went through her notes after her funeral passed them on to his ex-student, who passed them on to her ex-student, whose post-graduate student would one day use some of her ideas to devise a new branch of mathematics.) The little boy who had a revelation one day about how changing the lengths of pieces of Meccano here and here in his crane made it lift much bigger toys (he went on to revolutionise the design of artificial limbs). The father who never had the opportunity to study beyond high school, but encouraged his children's curiosity, and helped them set up 'research' projects in the garden (his son went on to develop high-protein drought-resistant food crops, while his daughter became a world authority in anti-metastatic drugs derived from plant extracts.) The girl who demanded endlessly of her grandfather to know how worms worked (her work in neuroscience would be fundamental to the eventual development of early diagnosis and mitigation of Alzheimer's disease.) The teenager who was fascinated by the way the exhaust gas from his father's car moved in the fog on cold mornings when it was within a certain distance of the garage wall (his fluid engineering thesis would one day be the basis for the complete re-design of aeronautical turbine engines).

From the tiniest microscopic fungus, to the furthest flung corners of the universe, every part of his Father's creation was important to somebody – somewhere, a human being wanted to know. In their limited, stumbling but determined human way, they wanted to understand. And Castiel loved them for it. Homo percuriosus, indeed.

However, he drew the line at cruelty.

"I do not care for Herr Professor Schrodinger's methods," he announced curtly one day, when Sam's research on a job led to a discussion of the scientific method that humans had to employ, not having the angelic capacity for knowledge that Castiel enjoyed. "I cannot condone such treatment of a living, feeling creature."

"It was never a real cat, Cas," Sam explained, "It was a thought experiment, a fictitious scenario to explain a concept – you cannot know what the state of the cat is without opening the box to look."

Castiel cocked his head. "The state of a cat put into a box is usually best described as somewhere between 'extremely unhappy' and 'homicidal'," he noted, thinking of cats he had seen in carry crates. Veterinary surgeons were some of the bravest people on the planet, to confront that sort of annoyance in a species that had at least two paws in Hell from birth.

Sam sighed. "Look, it's about modelling how things are, and how things work," he tried again. "Your model is only as good as your assumptions, and your assumptions are only as good as your information. Like what I'm doing here. I can make assumptions based on past experience, but I need as much information as possible to come up with as accurate a final calculation as I can get about what it is that's causing the disappearances."

A look of understanding dawned on Castiel's face. "So, your research for a Hunt is very much like doing science," he decided.

Sam smiled. "Yes, in many ways. I think I've got this one just about worked out…"

"You find the process… intellectually gratifying." It was an observation, rather than a question.

"Yeah, I guess I do," Sam agreed. "See? You just did it yourself, there. You made some assumptions, based on what you know about me, throw in some information from this conversation, and your conclusion is pretty accurate."

Castiel looked thoughtful, and realised that Sam was right; he had done exactly that. Not used his 'angel mojo', as Dean called it – he had used the human scientific method. "Thank you, Sam," he said quietly, "This has been very interesting." Still looking thoughtful, he disappeared in a flap of trench coat.

...oooooOOOOOooooo... ...oooooOOOOOooooo... ...oooooOOOOOooooo...

The Winchesters didn't find out just how interesting he'd found it until a week later.

Castiel had procured a notebook computer, and asked Sam's assistance in setting it up. He then settled into the corner of their cruddy motel room.

"Er, why the sudden foray into the electronic age?" asked Dean, running his knife across the whetstone.

"With my own computer, I will be able to assist Sam with research matters, according to the principles of the scientific method," he announced. "Also," he added, "I am working on a small research project of my own. I had no idea how gratifying and… intellectually fulfilling the challenge would be," he added, a little shyly. "I believe I now have an insight into why so many humans work in the sciences for what is comparatively poor remuneration. Knowledge is what is important to them. It is a noble sentiment."

"Er, okay," agreed Sam, setting the angel to checking some information on a Births, Deaths and Marriages database.

"This is great, Sammy," grinned Dean, "You have yourself a research assistant! A PA! Pity he couldn't be a hot chick in a short skirt. So, what is this project of your own, Cas? Designing a better trench coat? Investigating the effects of alcohol on angel physiology? Working out how many angels can dance on the head of a pin?"

"Thomas Aquinas used the 'angels on the head of a pin' expression as a philosophical metaphor to ridicule the wasting of time in debating subjects of no practical value," Castiel told him. "However, if we were to apply the scientific method, it would be necessary to make certain assumptions to construct the model. For instance, the space taken up by a dancing angel will depend on the size that the angel has assumed – let us propose that, for the sake of this argument, the angels have decided to take protozoa as their vessels, so that they can fit onto the head of a pin. Further, it will depend on the type of dance the angels wish to perform: Irish dancing is performed with the arms held close to the body, whereas if they were to dance in the style known as krumping, each angel would require more space, to wave its flagellae around in rapid motion. If the angel-protozoa wished to perform a partnered dance, such as a grand waltz, in which a couple travels across a two-dimensional plane while dancing…"

"Hey, Dr Bunsen Honeydew," Dean said to Sam, "I think your Beaker is speaking Enochian. He's easier to understand when he just goes 'Meep meep meep', then explodes."

"What is your research project, Cas?" asked Sam curiously, hoping it was nothing to do with cats in boxes.

Castiel didn't lift his eyes from his screen. "I am attempting to calculate how many children Dean has."

That brought a sudden silence to the room.

"How many children I have?" asked Dean, his eyebrows rising.

"How many children you have," confirmed Castiel. Dean blinked a couple of times. "Of course," the angel continued, "It can only be an estimate. Using the scientific method, I have constructed a model for calculation but the model is only as good as the assumptions, and the assumptions can only be as good as the accuracy of the information used to justify them."

Dean frowned at his brother. "Sam," he rumbled quietly, "What sort of crap have you been filling his head with? Cas, what have I told you about the dangers of talking to geeks?"

"What sort of assumptions?" asked Sam, morbidly fascinated.

"Assumptions about Dean's behaviour, constructed from what I know of him, rather than using my 'angel mojo'. For instance, how old were you when you lost your virginity, Dean?" the angel asked matter-of-factly. Dean bristled.

"I don't see how that's any of your damned business," he replied abruptly.

"Would it have been eighteen, or nineteen? I shall use nineteen, to be conservative, in accordance with the principles of the scientific method…"

"I was fifteen!" corrected Dean grumpily, his mouth going into gear before his brain. Sam looked at him incredulously. "Hey, don't look at me like that, bro, she was insulting my virility…"

"Dean, that's not legal in most northern states!" yelped Sam.

"It's cool, dude, she was fifteen too, and I sure as hell wasn't her first," said Dean smugly, with a trademark smirk. Castiel tapped a correction into his notebook.

"It is not prosecutable if two teenagers of the same age are having consensual intercourse," he said equably, "And there is nothing unusual about losing virginity at fifteen. A mathematical calculation I have located on the internet puts the average age at seventeen." Dean pulled a face of vindication at Sam as Cas peered at the screen. "Now, Dean, once you started having sex, how many partners would you say you average per calendar month? An informed estimate will be sufficient."

"Hey, I thought I'd just said that my private life is none of your damned business!" Dean was immediately bristling again. Castiel regarded him serenely.

"Dean, we all know that you enjoy fornication. A lot. All I am attempting to do is to use data that is as accurate as possible." He turned to Sam. "Sam, how many partners would you estimate your brother averages per calendar month?"

Sam looked nonplussed. "Er, well, I don't follow him around counting, when he goes out looking for company," he stammered, "And I, um, don't ask him about it afterwards – I have trouble getting him NOT to tell me, 'Bro, too much information!', I say, but sometimes he's determined to tell me about it anyway…"

"Hey! I'm trying to educate you!" put in Dean, "Because you need to get laid, Sammy, one day you'll thank me…"

"… So mostly, I try not to think about it. Er." finished Sam.

Castiel frowned thoughtfully. "I shall modify my model to include a 'Too Much Information Factor'… bearing in mind the effect that an estimate will have on the model, would you agree that three per calendar month would be a conservative estimate?"

Sam nodded slowly. "Yeah, yeah, three sounds about right, that would make sense…"

"Hey, I get at least twice that!" Dean burst out. "Three a week, is more like it, and that's not including…" he suddenly petered out to a halt as the other two looked at him curiously. "It's not my fault if Sam can't handle having a Living Sex God as a big brother," he declared sniffily. Castiel tapped the keyboard.

"Thank you, that helps," he said, not looking up, "Now, when you partner with a woman for an evening of fornication, what is the usual frequency of copulation?"

Dean looked at the angel, and blinked a couple of times. "Um… I have no idea what you said, but it's probably none of your damned business."

"He means how many times do you do it with each chick, Dean," translated Sam, taking an interest in the proceedings.

"I was right!" said Dean, "It IS something that's none of your damned business!"

"Please try to remain calm, Dean," said Castiel, "You are not compelled to answer, I merely wish to apply the scientific method as rigorously as possible." He pecked at the keys. "I shall put 'one', to be on the conservative side."

"Twice. At least." corrected Dean with a grumpy sneer. "Living Sex God, remember?" Sam made a strangled snorting noise and continued with his valiant attempt to look like he was still reading the screen in front of him.

Castiel seemed pleased with his calculations. "This is gratifying, we are making progress."

"Cas," growled Dean, "You can stop right there, I am NOT answering any more questions about my sex life, you perv!"

"Have you not considered viewing this as an opportunity to brag?" asked Castiel, with a tilt of his head. Sam made a snorting laughing noise, but stifled it quickly into a cough when Dean's withering stare fell on him.

"Very well. I shall not press you further for data regarding my research," conceded Castiel, sounding just a little hurt. He was silent for half a minute, tapping away, then he spoke up again. "I am assuming that the majority of your partners are female. At least 95 percent of them."

"ALL OF THEM!" thundered Dean, glaring murderously at Castiel, who said "Thank you" quietly and went on serenely computing. "What've you done to him, Sam?" fumed Dean, "This is NOT the blushing vanilla angel of untainted virtue who got us thrown out of a Den Of Iniquity. He's become a disgusting perv with an unhealthy fascination for other people's sex lives!"

"Hey, he was like this when I found him," protested Sam.

"Not other people's, Dean, just yours," clarified Castiel, "And I am not interested in your sex life, per se, I am merely concerned with collecting information that is as accurate as possible in order to calculate how many children you probably have." The angel looked at him calmly. "I am not making any judgements, Dean, just calculations."

"Why? For God's sake, WHY? Why the fuck do you care how many children I may or may not have?" he asked.

"It is a fascinating insight into the scientific method employed by humans," Castiel answered him "I am gaining a new appreciation for the intellectual capacity and endeavours of my Father's creations. In addition, you have told me on numerous occasions that I should get a hobby."

"How about crochet? Or scrapbooking? Quilting trench coats?" suggested Dean, his voice taking on an edge of shrillness, "Collecting buttons? Train spotting? Seeing how many pool balls you can fit into your mouth at once?"

"That would be a pointless pursuit for an angel," Castiel told him, "As I could 'cheat', and take a hippopotamus for a vessel. Do you use barrier contraception every time you have sex, or do you leave contraception to the woman?"

"Oh, he's always sensible about that," chirped Sam, "Dad was realistic enough to guess what he was up to, and made sure he knew about condoms early on in the piece, besides which, you'd never know it, but Dean actually has a responsible streak in him when it comes to…

"SAAAAM!" Dean shrieked at his brother.

Sam fell silent, turning on the puppy-dog eyes. "I'm just saying you try to be a considerate partner and a responsible adult, and you always have a box of…"

"SAAAAM!"

"Just trying to help," mumbled Sam in a hurt tone. Dean turned the Death Glare on him as Castiel adjusted his numbers.

"Thank you Sam. Have you ever had to take him to a doctor, clinic or medical treatment facility with symptoms of an…"

"Sam." Dean's voice was venomously quiet. "Sam, if you answer that question, in any way at all, I will take this knife," and he brandished the knife he was sharpening, "And give you a haircut that will make Uncle Fester look like Cousin Itt by comparison. Capiche?"

Sam closed his mouth, and looked apologetically at Castiel. The angel came perilously close to an expression suggesting disappointment. "Cas," said Sam, "I think perhaps Dean would like you to stop asking… prurient questions."

The angel cocked his head. "I do not understand why you would take offence at a rigorous application of the scientific method," he told Dean, looking confused, "Your habit of wishing to relate the details of your sexual encounters to your brother in explicit language, which in fact let to the inclusion of the 'Too Much Information Factor' in my calculations, suggests that this is not information about which you are shy. Indeed, you seem to derive a certain relish from informing Sam of…"

"That's different!" snapped Dean. "He needs to know! It's educational! As his big brother, it is my duty to take any and all actions I see fit in order to get him laid! And that means making sure he has as much information as possible to help him!"

Castiel looked knowing. "So, in fact, you apply the principles of the scientific method to your quest to have your brother engage in intercourse," he nodded in understanding.

"I think we have some holy oil in the trunk, just enough for a Cas-sized Molotov, provided he stays in a human vessel and doesn't 'cheat' by taking a hippo…" muttered Dean.

"Oh, God," sighed Sam, dropping his head to bang into the table before him. "Kill me now…" He sat up. "I think perhaps it would be best if you dropped this line of enquiry, Cas," he suggested, "Humans can be a bit… touchy about that sort of thing. It's like, it's like personal space, it's hard to know which humans are going to have what limits... Just recognise that as someone who hasn't been brought up human, you'll probably have trouble working out where those acceptable limits are, okay?"

"Very well," agreed Castiel amiably.

"Right. Right," Sam exhaled in relief. "Here, could you cross-check this for me, while you're here…"

Dean subsided. Castiel desisted. The research continued.

The quiet clicking of keys and the stropping of the knife on the stone filled the room with companionable silence for a while. Then…

"Seven point three", announced Castiel.

The Winchesters looked up, bewildered.

"What?" asked Sam..

"Seven point three," repeated Castiel.

"Seven point three what?" asked Dean.

"Children," replied Castiel, "I have calculated that you probably have seven point three children. Out there. Somewhere." He waved a hand vaguely. "I do not have enough information to postulate where. There are limits to the scientific method."

Dean let his head fall to the table. "Cas," he mumbled into the tablecloth, "You need to get another hobby."

"Point three? Point three?" said Sam, looking confused, "How can you have 'point three' of a child? Either a child exists, or it doesn't. You can't have one third of a child."

"It is only an estimation," clarified Castiel, "That point three would be rounded down to the nearest whole number, seven. Or," he continued thoughtfully, "Perhaps it means that there is a woman out there who is now at three months' gestation. Depending on whom Dean was fornicating with approximately three months ago."

Sam and Castiel looked at Dean speculatively.

Dean put down the knife, and picked up his jacket and keys. "I'm going out," he announced grumpily, "Don't wait up, Sam."

"Where are you going?" his brother asked.

"To mess with Einstein here and his mathematical model!" snarked Dean, slamming the door.

Castiel's face fell. "I do not think Dean is at all appreciative of the intellectual stimulation or profound gratification that the scientific method has to offer," he observed to Sam.

"Yeah, I think you'll find he's more interested in less high-brow forms of stimulation and gratification," agreed Sam sympathetically. The angel looked so disappointed, he felt an obligation to try to cheer him up. "Look, it's great that you've decided to learn more about this aspect of humanity. If you want to pursue this, it might be better if you stick to researching with me in future, okay?"

Castiel brightened up, and smiled gratefully. "Thank you, Sam," he said, turning back to his notebook, "Shall we start now?"

"Yeah, we'll have some peace and quiet without Dean around to annoy the intellectuals," joked Sam.

"That will facilitate the process considerably, I am sure," agreed Castiel.

Sam turned back to his own laptop. He'd located a report on a newspaper site requiring verification. Cas could follow that up for him whilst he tracked down a coroner's report…

Before he could relay this request, the angel sat up, with an expression of earnest scientific enquiry on his face, and asked,

"So, Sam, how old were you when you lost your virginity?"

Reviews are the Fascinating Cell Colonies in the Petri Dish OF Life!

And to the wretches who want to know what happened when Dean became pruriently curious about what it's like to have sex with a werewolf, as mentioned in passing in the last explanatory chapter of 'Prince Charming': I curse your plot bunnies and the camel they rode in on! *shakes fist*.