Page 200 - Deep Learning

The Growth of Competence 183

task is to draw a map of the world, that same proposition forces you to choose
some projection of the spherical surface of the Earth onto the flat surface of
the map, a problem that does not arise for people who believe in a flat Earth,
but it does not specify which projection is best. if you want your map to exhibit
geographic areas in their correct proportions, use a Sylvanus projection, but if
you, like sailors, want your rhumb lines – courses of constant compass bear-
ing – to appear on the map as straight lines, use Mercator’s projection. The
belief that the Earth is round does not specify or recommend any particular
action, but it can be used to reason about action in an infinitude of situations,
most of them not contemplated at the time in life when this belief is adopted.
practical knowledge, in contrast, specifies which action or actions to
perform to solve some task. If you want the elevator to come, push the button
is a prototypical example. Actions must be adapted to the situation at hand if
they are to be effective, so practical knowledge must include knowledge of the
conditions under which an action should be performed and the conditions
under which it should not. if you are at an intersection and the traffic light is
red, you are supposed to stop; if the light is green, to keep going. in most cases,
the contingency of action is more intricate and complex than this example,
but the principle is the same: An action is appropriate under some conditions
but not under others. to be competent, to know what to do, is to know when,
under which conditions, to do what.
These observations imply that the smallest unit of practical knowledge
is a three-way association between a goal, a situation (or a class of situations)
and an action (or action type). For historical reasons, such three-way associa-
tions between goals, situations and actions are called production rules, or rules
for short. The term “rule” inconveniently confuses implicit knowledge in a
21
person’s head with explicitly codified entities like traffic laws, but the usage is
too entrenched in cognitive science to escape. We can represent a rule in the
following schematic way:
Rule: Goal, Situation  Action,

which is a shorthand for the hypothesis that the person whose rule it is, when
pursuing the specified goal and finding himself in a situation of the specified
type, will consider the action mentioned in the right-hand side of the rule. The
situation is assumed to be specified as a conjunction of features (the water is
boiling and the tea leaves are in the strainer and the strainer has been placed in
the cup …). A three-way association is an atom of practical knowledge that
cannot be split into smaller parts that themselves are meaningful units of
practical knowledge. The hypothesis that practical knowledge is represented