What is Computer Science?

Slides for MIT's course on "Structure and Interpretation of Computer Programs" is available on line. The first few slides talk about a key issue that I think is important in understanding the Computer Science and Software in general:

This first thing we need to do is discuss the focus of 6.001. What is this course all about? This seems quite obvious -- this is a course about computer science. But we are going to claim in a rather strange way that this is not really true.

First of all, it is not really about science. It is really much more about engineering or art than it is about science.

...and it is not really about computers. Now that definitely sounds strange! But let me tell you why I claim it is not really about computers. I claim it is not really about computers in the same way that physics is not really just about particle
accelerators, or biology is not really just about microscopes, or geometry is not really about surveying instruments.

In fact, geometry is a good analogy to use here. It has also a terrible name, which comes from two words: GHIA or earth, and METRA or measurement. And to the ancient Egyptians, that is exactly what geometry was -- instruments for measuring the earth, or surveying. Thousands of years ago, the Nile annually flooded, and eventually retreated, wiping out most of the identifying landmarks. It also deposited rich soil in its wake, making the land that it flooded very valuable, but also very hard to keep track of. As a consequence, the Egyptian priesthood had to arbitrate the restoration of land boundaries after the annual flooding. Since there were no landmarks, they needed a better way of determining boundaries, and they invented geometry, or earth measuring. Hence, to the Egyptians, geometry was surveying -- and about surveying instruments. This is a common effect. When a field is just getting started, it’s easy to confuse the essence of the field with its tools, because we usually understand the tools much less well in the infancy of an area. In hindsight, we realize that the important essence of what the Egyptians did was to formalize the notions of space and time which later led to axiomatic methods for dealing with declarative, or What Is kinds of knowledge. --- So geometry not really about measuring devices, but rather about declarative knowledge.

So geometry is not really about surveying, it is actually fundamentally about axioms for dealing with a particular kind of knowledge, known as Declarative, or "what is true" knowledge.

By analogy to geometry, Computer Science is not really about computers -- it is not about the tool. It is actually about the kind of knowledge that computer science makes available to us.