Science promises discovery. Great industries and great nations
spend huge sums of money hoping that further discoveries will
make them richer and more powerful. Publishers and broadcast-
ers retail news to audiences eager to share in the adventure and the
profits of scientific discovery. Philosophy promises understanding.
But, what makes us say that we understand this or that idea? What
makes us say that students understand? Is it that they can repeat back
what they have heard or read, that they can pass examinations, that
they say they understand? Those who promise adventure, profit,
power, must have something concrete to offer: mushroom-shaped
clouds, moon rocks, chess-playing machines. Where philosophy can
be lofty and noble, science must be crass and materialistic.

Scientists must work with practical possibilities rather than ideals.
All experiments are flawed, but they are not all equally flawed. Some
are much better than others. There are significant degrees of difference
between disciplined, publicly verifiable observation and ordinary, sub-
jective experience. Several hundred years of scientific history have
demonstrated that each level of improvement is well worth the effort.
The whole structure rests on operational definitions.

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