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MIT OpenCourseWare

http://ocw.mit.edu

6.001 Structure and Interpretation of Computer Programs, Spring 2005

Transcript – 1A: Overview and Introduction to Lisp

[MUSIC PLAYING] PROFESSOR: I'd like to welcome you to this course on computer science.

Actually, that's a terrible way to start. Computer science is a terrible name for this business.

First of all, it's not a science. It might be engineering or it might be art, but we'll actually

see that computer so-called science actually has a lot in common with magic, and we'll see

that in this course.

So it's not a science. It's also not really very much about computers. And it's not about

computers in the same sense that physics is not really about particle accelerators, and

biology is not really about microscopes and petri dishes. And it's not about computers in the

same sense that geometry is not really about using surveying instruments.

In fact, there's a lot of commonality between computer science and geometry. Geometry,

first of all, is another subject with a lousy name. The name comes from Gaia, meaning the

Earth, and metron, meaning to measure. Geometry originally meant measuring the Earth or

surveying.

And the reason for that was that, thousands of years ago, the Egyptian priesthood

developed the rudiments of geometry in order to figure out how to restore the boundaries of

fields that were destroyed in the annual flooding of the Nile. And to the Egyptians who did

that, geometry really was the use of surveying instruments.

Now, the reason that we think computer science is about computers is pretty much the

same reason that the Egyptians thought geometry was about surveying instruments. And

that is, when some field is just getting started and you don't really understand it very well,

it's very easy to confuse the essence of what you're doing with the tools that you use. And

indeed, on some absolute scale of things, we probably know less about the essence of

computer science than the ancient Egyptians really knew about geometry.

Well, what do I mean by the essence of computer science? What do I mean by the essence

of geometry? See, it's certainly true that these Egyptians went off and used surveying

instruments, but when we look back on them after a couple of thousand years, we say, gee,

what they were doing, the important stuff they were doing, was to begin to formalize

notions about space and time, to start a way of talking about mathematical truths formally. That led to the axiomatic method. That led to sort of all of modern mathematics, figuring

out a way to talk precisely about so-called declarative knowledge, what is true.

Well, similarly, I think in the future people will look back and say, yes, those primitives in

the 20th century were fiddling around with these gadgets called computers, but really what

they were doing is starting to learn how to formalize intuitions about process, how to do

things, starting to develop a way to talk precisely about how-to knowledge, as opposed to

geometry that talks about what is true.

Let me give you an example of that. Let's take a look. Here is a piece of mathematics that

says what a square root is. The square root of X is the number Y, such that Y squared is

equal to X and Y is greater than 0. Now, that's a fine piece of mathematics, but just telling

you what a square root is doesn't really say anything about how you might go out and find

one.

http://ocw.mit.edu

6.001 Structure and Interpretation of Computer Programs, Spring 2005

Transcript – 1A: Overview and Introduction to Lisp

[MUSIC PLAYING] PROFESSOR: I'd like to welcome you to this course on computer science.

Actually, that's a terrible way to start. Computer science is a terrible name for this business.

First of all, it's not a science. It might be engineering or it might be art, but we'll actually

see that computer so-called science actually has a lot in common with magic, and we'll see

that in this course.

So it's not a science. It's also not really very much about computers. And it's not about

computers in the same sense that physics is not really about particle accelerators, and

biology is not really about microscopes and petri dishes. And it's not about computers in the

same sense that geometry is not really about using surveying instruments.

In fact, there's a lot of commonality between computer science and geometry. Geometry,

first of all, is another subject with a lousy name. The name comes from Gaia, meaning the

Earth, and metron, meaning to measure. Geometry originally meant measuring the Earth or

surveying.

And the reason for that was that, thousands of years ago, the Egyptian priesthood

developed the rudiments of geometry in order to figure out how to restore the boundaries of

fields that were destroyed in the annual flooding of the Nile. And to the Egyptians who did

that, geometry really was the use of surveying instruments.

Now, the reason that we think computer science is about computers is pretty much the

same reason that the Egyptians thought geometry was about surveying instruments. And

that is, when some field is just getting started and you don't really understand it very well,

it's very easy to confuse the essence of what you're doing with the tools that you use. And

indeed, on some absolute scale of things, we probably know less about the essence of

computer science than the ancient Egyptians really knew about geometry.

Well, what do I mean by the essence of computer science? What do I mean by the essence

of geometry? See, it's certainly true that these Egyptians went off and used surveying

instruments, but when we look back on them after a couple of thousand years, we say, gee,

what they were doing, the important stuff they were doing, was to begin to formalize

notions about space and time, to start a way of talking about mathematical truths formally. That led to the axiomatic method. That led to sort of all of modern mathematics, figuring

out a way to talk precisely about so-called declarative knowledge, what is true.

Well, similarly, I think in the future people will look back and say, yes, those primitives in

the 20th century were fiddling around with these gadgets called computers, but really what

they were doing is starting to learn how to formalize intuitions about process, how to do

things, starting to develop a way to talk precisely about how-to knowledge, as opposed to

geometry that talks about what is true.

Let me give you an example of that. Let's take a look. Here is a piece of mathematics that

says what a square root is. The square root of X is the number Y, such that Y squared is

equal to X and Y is greater than 0. Now, that's a fine piece of mathematics, but just telling

you what a square root is doesn't really say anything about how you might go out and find

one.

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