Sometimes he wonders if they're right, if he nothing more than a machine, an automaton. Unfeeling. Uncaring. Unworthy. Inhuman. He wonders if his pale skin hides turning cogs and gears. He wonders if there is a heart in his chest, or if the hollowness he feels there marks a lack of one. He has a pulse, however, so perhaps it's simply as robotic as the rest of him, serving only to keep the machine running. Vaguely, he wonders why emotions are associated with the heart when they are controlled in the brain. He supposes that his misunderstanding of such thing merely proves he is not human, not normal.
A freak.
He wonders if blood or oil would ooze from a wound, should one afflict him. He wants to find out, wants to experiment. After all, machines are to be tinkered with, yes? Why not tinker with himself, experiment and test and all other manner of things? He wouldn't feel it. Machines are incapable of feeling, and so is he.
John isn't home, so he is free to snatch a knife from the kitchen, sitting at the table before rolling up his shirtsleeve, exposing the white flesh of his inner arm. He reckons that, as he is a machine, he will need to use a rather large amount of force to pierce the armour plating that is undoubtedly protecting the wires and cogs and gears and machinery, as that is what machines are composed of. So he does. And he most certainly doesn't gasp at the bite of the blade, doesn't made a sound when it sinks in deep and black spills out around it, stark against the skin which has suddenly become quite shiny indeed, silvery almost. Metallic. The black flows quickly, coating the blade when he pulls it out and calmly places it beside him. Small puddles of it begin to form on either side of his arm, the oil seeping, flowing, streaming, and he wants it to stop because he dislikes this evidence, this irrefutable proof of his lack of humanity.
His breath comes in short, sharp pants, and he wonders what his supposed lungs are. Are they anything? Do they exist? After all, with a chest so hollow as his, there mustn't be much in it. Perhaps it is merely a show, something he subconsciously puts on to blend in? Perhaps he doesn't have to breathe at all? He likes that idea, and decides to stop his panting. It's quieter that way. He silently congratulates whatever maker he has. His machine runs quietly when not breathing. He likes the quiet, even if it makes the drip, drip, drip of oil on the tabletop even louder.
He feels something wet on his face, and uses his uninjured arm to reach up and dab at it. His fingers come away black, and he realises he is crying, black dribbling from his eyes, down his cheeks, marring the white. It trickles over his lips and he can taste it, horrid and awful and he wants to vomit, but machines cannot do so, as they have no stomachs. He wants to laugh; he has an excuse to stop eating for good.
A slam. A shout. He nearly jumps at the suddenness of it, the shattering of the near-silence that he was happy to be blanketed in. He is almost irked, but machines cannot feel, therefore the point is moot.
There is warmth now, on his cheeks, on his arms, and a volley of curses from a familiar voice. John.
He wants to laugh, and so he does, his steel vocal chords grinding together to create a coarse chuckle. He gestures to the oil, on both his face and his arm, and whispers the name of the dark substance, another laugh produced. Oil. Machine. Freak. Wrong.
The doctor's face falls as he shakes his head, warmth cupping his cheek as he softly denies it. No. Blood and tears. Human. Sherlock.
And Sherlock is so jolted by the gentleness, the tenderness, that he looks down and sees not black, but vivid red. Blood. Fingers touch his cheek and find clear liquid, and when he licks his lips he finds the taste salty. And pain. Oh God, pain from the arm that he sees is very un-metallic. This is a bit not good, he thinks.
He is cleaned and bandaged and shown by John that he isn't, in fact, a machine, as machines cannot love and be loved, cannot cry and laugh and smile and frown and feel anger and pain and loss and joy.
He is not a machine, not a freak. He is Sherlock Holmes.