If Sherlock Holmes was anything, he was logical. Inquisitive, yes. Cool? Calculating? Collected? Yes, yes, and always. But most of all, what Sherlock was, and what Sherlock considered himself to be above all else, was a logical being. A brain is all one has in the end, is it not? Thoughts and rationality, those were privileges, and anyone who thought otherwise— well, they weren't really thinking at all, were they? Funny, the things people took for granted.
Now there was someone else, someone… not like him, no, no one was like him. But someone whose first words to the consulting detective hadn't been "Piss off," or any variation thereupon. It hadn't even been negative. No, here was someone Sherlock was coming to like, and not just coming to find useful for being handed a pen here and there or picking up the grocery, and not coming to find unfortunately necessary like Detective Inspector Lestrade, but to actually like.
What had that been earlier, had they actually been laughing? Sometimes Sherlock sneered and sometimes Sherlock smiled but he rarely laughed in earnest. He could fake laughter with the rest of them—scratch that—better than the rest of them. But this wasn't a game, this wasn't a manipulation or a ploy, this was— Sherlock could almost pretend he didn't know.
Of course no one would want Sherlock Holmes as a flatmate, quite frankly no one would want him, well, anywhere around unless it was absolutely required. This, Sherlock was used to. He reacted well to aversion and even preferred it, a happy recluse. But he could see how having someone around would be a pleasant change. Of course this would lead to problems, there were always problems when other people were involved, it befuddled him as to why every one of them felt it was necessary to fling their emotions around like dirty laundering for everyone to see. Emotions were illogical. Emotions sucked up rationality. Those pesky things, he could always do without.
People were like food, they slowed him down. Nothing could be allowed to slow Sherlock down when he was working. No attachments, that had always been the rule. Science didn't have time for slowpokes and everyone was already two steps behind. But even still, he felt, in that place his brain stored thoughts that were most unprudent, that this army doctor was something different. John had saved his life. John was experienced. Sherlock rather liked the way he could almost see the dribble coming down from the soldier's mouth when was amidst one of his—okay, admittedly showy—scientific deductions. But perhaps most important of all, John had a cellular phone. Try to shake it off as he may, the game, however illogical, was on.