He sees the world as a system which, given enough time and effort, is completely knowable. This is a fragile illusion that your nerd has adopted, but it’s a pleasant one that gets your nerd through the day. When the illusion is broken, you are going to discover that…For the uninitiated:
Your nerd has control issues. Your nerd lives in a monospaced typeface world. Whereas everyone else is traipsing around picking dazzling fonts to describe their world, your nerd has carefully selected a monospace typeface, which he avidly uses to manipulate the world deftly via a command line interface while the rest fumble around with a mouse.
The reason for this typeface selection is, of course, practicality. Monospace typefaces have a knowable width. Ten letters on one line are same width as ten other letters, which puts the world into a pleasant grid construction where X and Y mean something.
This is an example of a monospaced font in action. Notice the way the letters line up; this is what most typewriters produced, back in the day. Monospaced fonts are useful for making ASCII art like this:
___________________ _-_ \==============_=_/ ____.---'---`---.____ \_ \ \----._________.----/ \ \ / / `-_-' __,--`.`-'..'-_ /____ || `--.____,-'
... but being significantly less readable than the proportional fonts that post-Mac computers have made us accustomed to seeing, they're not good for much else. Unless you have a certain frame of mind which requires a certain kind of order.
For the record, I held onto monospaced fonts for my email for a little while — how else could I be sure I was seeing a .sig as intended? — but I'm not geeky enough to use them any more.