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C00002 00002	common[f82,jmc]		What is common sense?
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common[f82,jmc]		What is common sense?

"Common sense should not be confused with %2common opinions%1, namely the
beliefs we can readily formulate when asked: these are often false
overgeneralisations or merely the result of prejudice.  Common sense
is a rich and profound store of information, not about laws, but about
what people are capable of doing, thinking or experiencing.  But common
sense, like our knowledge of the grammar of our native language, is hard
to get at and articulate, which is one reason why so much of philosophy,
psychology and social science is vapid, or simply false". - Aaron
Sloman in the introduction to his book 
"The Computer Revolution in Philosophy".

	It is now widely agreed among AI researchers that understanding
common sense knowledge and reasoning is a key problem.
Although many "ecological niches" exist for expert systems without
common sense, present programs are limited and brittle.

Here are some of the components of common sense as I see it.

1. The ability to represent declarative knowledge in a way independent
of particular goals and to use this knowledge in pursuit of whatever
goals it may be relevant to.  Both knowledge of particular situations
and general knowledge expressed by quantified sentences are required.

2. Knowledge of events occurring in time, of situations or partial
situations and partial knowledge of situations.  The effects of
actions and other events.

3. Facts about goals and their achievement.  Even when the goals are
intellectual, e.g. the solution of a mathematics problem, time,
events and actions are involved in their achievement.

4. Concurrent events.

5. Other people, their knowledge, beliefs and goals.  Other attitudes
such as hopes and fears, likes and dislikes.

6. Space and objects in space, their persistence in time, their creation
and destruction.  Extended objects, shapes.  Rigid and flexible objects.
Substances.

7. Quantities and measurement.

8. The world described by science and its connection with the
world as described by common sense.

9. Epistemology.  A theory of how knowledge is obtained.

10. Communication.  How utterances are to be understood as making assertions.
How the behavior of other people is affected by communication.

	It seems to be a formidable task to build a computer program
with all the above abilities.  Perhaps they can be arranged in a tree
so that one can make programs with the more basic capabilities and
debug them, leaving the others for later.

dec 6

	It is worthwhile to distinguish levels of thinking.

Level 1 - Situation → action, e.g. by a production rule.

Level 2 - Direct planning. Goal ∧ situation → action, but action
has preconditions forming subgoals.

Level 3 - When direct planning loses, then there arises the goal
of forming a plan.

	Perhaps the second of these is the prolog level.  The higher levels
may be implemented by applying a lower level method to a database
that includes meta level information.