Howie's two worlds

Howie's life consists of two worlds: the inner world (the soup of internal thoughts, ideas, and insights that he garners throughout his life) and the outer world (the physical world that he interacts with - his home, the subway, the streets, his workplace, other people). These two worlds are almost completely insulated from each other in that, even if Howie's outer world (physical lifestyle) stays unchanging, the inner world is undergoing dynamic growth as Howie makes new connections and observations about the world. Then, comes the question, which world is more real for Howie? (Short answer: The inner world)

In the perspective of Howie, the outer world is a specimen that nourishes his elaborate inner world of thoughts, questions, analogies, historical accounts, ideas, and theories. He even develops theories and conducts experiments (ex. testing the shoelace flexion model) to develop a comprehensive internal understanding of the physical world. Beyond this purpose of a "specimen", however, things happening in the outer world don't really directly affect Howie's inner feelings or emotions (I'll be contradicting this point in the next paragraph). For example, we never really (feel free to correct me on this) hear Howie expressing his emotions about something that happened in the real world, we just hear him making observations. On the other hand, we see bursts of exclamation marks and italicized words as the narrator internally praises some industrial design or passionately describes the history of an everyday object. What fires up Howie's excitement and joy (the predominant emotions throughout the book) are the thoughts he has in the inner world.

Yet, it's not accurate to judge Howie as someone wholly immersed in his inner world and disconnected from his physical life. He does experience emotions through his social interaction with other people in his life: he feels diminished that how his friends are smarter and more capable than him, and he walks away from the escalator to avoid the awkwardness of encountering the person riding it. From this and the previous paragraph, we can conclude that Howie is straddling a line between his inner and outer worlds. More precisely, he switches back and forth between the two worlds such that he defaults to living in his "inner world", but he is sometimes interrupted from his ponderings and forced to engage in the outer world (ex. seeing the person writing the escalator --> walking away from the escalator) and soon comes back to the inner world.

An interesting thing about the inner-outer world system is that L also has her own “inner world” and the inner worlds of L and Howie characters interact with each other. On page129, we learn that L’s conversation with Howie about a riddle that has been occupying her inner world of thoughts leads the same riddle to pop up in Howie’s mind. It's important to point out that this exchange of “inner worlds” doesn’t happen with any other character in the book - the other interactions Howie has with other humans are more superficial/shallow/physical than an intellectual exchange. This intimacy of exchange of inner worlds is perhaps why L is such a special person to him (I mean, he thinks about L 580 times a year - more than once every day). 

TL;DR:

The center of Howie’s life is on the inner world consisting of his internal thoughts, ideas, knowledge, and other media of mental exploration to better understand the outer world. The outer world is merely a subject of interest that Howie explores in his inner world, and the expansion and development of this inner world are what brings daily enjoyment (perhaps also the meaning of life) to Howie and makes L so special to him. 

Now the question is: so what? Why does this inner world-outer world have to do with our understanding of Howie/human behavior/philosophy? 

Current thoughts: the isolation of the inner world of Howie from the physical outer world indicates the level of “hollowness” that salary men/women would have felt at their workplace - distant from the things that these people find actually, internally interesting. On the flip side, this could also mean that these people who seem totally bored by the highly formal, repetitive lifestyle are actually internally incubating a world of excitement and curiosity.