Computer science is no more about computers than astronomy is about telescopes, biology is about microscopes or chemistry is about beakers and test tubes. Science is not about tools. It is about how we use them, and what we find out when we do.

In the good old days physicists repeated each other's experiments, just to be sure. Today they stick to FORTRAN, so that they can share each other's programs, bugs included.

LISP has jokingly been described as "the most intelligent way to misuse a computer." I think that description is a great compliment because it transmits the full flavour of liberation: it has assisted a number of our most gifted fellow humans in thinking previously impossible thoughts.

The purpose of abstraction is not to be vague, but to create a new semantic level in which one can be absolutely precise.

In this respect a program is like a poem: you cannot write a poem without writing it. Yet people talk about programming as if it were a production process and measure "programmer productivity" in terms of "number of lines of code produced". In so doing they book that number on the wrong side of the ledger: we should always refer to "the number of lines of code spent".

The prisoner falls in love with his chains.

The question of whether computers can think is like the question of whether submarines can swim.