You both feel that there is no purpose. That anything that renders mundane is pointless, even as such of basic human emotion.
*Autumn munched again on the pear, looking at Moriarty in deep thought. Obviously there was more than the intellectual admiration between the two men. Finally, Autumn came up with an answer.*
You both have the same perspective on humanity itself. Of life, of anything that humans strive for. Both of you separate yourselves from human interaction because you find the idea of living to be nothing more than just mechanical. You both feel that there is no purpose. That anything that renders mundane is pointless, even as such of basic human emotion.
Which is why you choose to not feel. You feel but you don't acknowledge. Why? I'll tell you why. *She leans over the table, pointing her finger at him.* Because emotions are your window of opportunity to manipulate. Manipulate one person through their emotions and you can have them crawling at your knees. Now you, you focus a lot on that. You like to feel on top.
Sherlock? I bet he likes that too but he doesn't do a thing about it because he doesn't share that same empowering motivation. But even so, he knows that emotions cause destruction. That man asked about the purpose of blushing. I had to explain to him on that.
Why? I don't know and not sure if I should care but if he didn't know what that meant, then obviously he himself is distancing away from basic human emotion and tries everything he can to not acknowledge it. You are fascinated by that because he is the only person, that you have met, to share that same vision.