1 Spanners: {showing off the new ship control software} This new astronavigation system is brilliant. It uses a revolutionary new location description system.
2 Spanners: It's so intuitive and logical; everything is where you expect it to be. You think, and it is.
3 Spanners: Thus what you think you see with your eyes, you actually grasp solely with your faculty of judgment, which is in your mind.
4 Iki Piki: Cool! What's it called?
4 Spanners: Descartesian coordinates.

If you understood that joke, you really don't need to read this annotation. Seriously.

René Descartes was a 17th century French philosopher and mathematician. His most influential contributions to these fields were:

1. The philosophical system formulated on the statement Cogito, ergo sum (I think, therefore I am), which supposes that data gathered by one's senses cannot always be trusted, so it is necessary to doubt everything. But the act of doubting implies that something ("I") is doing the doubting, and therefore that I exist. From this foundation, Descartes proceeded to the Wax Argument: When a piece of wax melts, all the sense data you have about it changes character, yet it is still the same object. So to know what something is, is an act of the mind, not the senses, or as Descartes put it: Thus what I thought I had seen with my eyes, I actually grasped solely with the faculty of judgment, which is in my mind.
2. The mathematical system known as Cartesian coordinates, which is a method of describing the locations of points in a space of any number of dimensions using numbers. This leads to the entire field of analytic geometry, in which geometry problems can be tackled using algebraic methods - in turn the basis of large slabs of mathematics such as calculus, metric spaces, vector spaces, differential equations, real analysis, measure theory, functional analysis, topology, and so on. And these things are pretty much the foundation of physics, and from there chemistry, biology, anthropology, psychology, sociology, and, inevitably, philosophy.

He was a pretty important guy, all things considered.

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2013-08-03 Rerun commentary: I wonder now if anybody got this joke at all the first time around without reading the annotation. I had to read it just now to remind myself!

Irregular Webcomic! Jokes so nerdy and obscure even the author doesn't get them!