Much of the excitement we get out of our work is that we don't really know what we are doing.

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.

The computing scientist's main challenge is not to get confused by the complexities of his own making.

It is a mistake to think that programmers wares are programs. Programmers have to produce trustworthy solutions and present it in the form of cogent arguments. Programs source code is just the accompanying material to which these arguments are to be applied to.

The effective exploitation of his powers of abstraction must be regarded as one of the most vital activities of a competent programmer.

In the software business there are many enterprises for which it is not clear that science can help them; that science should try is not clear either.

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