JMC@SU-AI.ARPA (07/17/84)
From: John McCarthy <JMC@SU-AI.ARPA>
[Forwarded from the Stanford bboard by Laws@SRI-AI. This reply
is in response to a request from David Cheriton@Navajo.]
jmc - As one of the importers of the first two terms from philosophy into
AI, I will say what I mean.
ontology - The dictionaries define it as the branch of philosophy that
studies what exists. In the bad old days, they argued about whether
physical objects, disembodied spirits, God, exist. Quine (1940s or 1950s?)
modernized the idea by saying that the ontology of a theory is the set
over which the bound variables range. As a nominalist he favored an
impoverished ontology, e.g. just because you want to predicate red(x),
doesn't mean that you need red or redness as an object. The AI
usage is derived from Quine's and remains quite close to it. The programs
or logical sentences have variables, and the ontology of the program
includes the sets from which these variables take values. For example,
Mycin includes bacteria in its ontology, because some of its variables
range over bacteria (the kinds of bacteria, not individual bacteriums),
but doesn't have doctors. It actually doesn't have patients either.
epistemology - In philosophy it means the study of knowledge, its sources
and limits. Again AI usage is derived from that and remains fairly
close. AI is more concerned than most philosophers with how the
knowledge is represented. AI is concerned with "epistemologically
adequate" internal languages for programs, i.e. languages that are
adequate for representing the knowledge that can actually be obtained
with given opportunities to observe and experiment. See McCarthy and
Hayes "Some philosophical problems from the standpoint of artificial
intelligence", Machine Intelligence 4, 1969.
teleology - I haven't used it in AI, so I can't speak precisely about
AI usage. In philosophy it means explaining things by ascribing
purpose to them. Extreme examples are, "The purpose of the rainbow
is to teach us that the next time God destroys the world it will be
by fire and not by water" and "The purpose of the ant is to teach us
not to be lazy". Teleological explanations were driven out of
biology accompanied by considerable squabbling. In AI the term
might be used to refer to goal-driven programs, but then it would
seem that the usage is further from the philosophical usage.pez@whuxle.UUCP (Paul Zeldin) (07/25/84)
Please note that not only has biology exiled teleology
but they have replaced it with teleonomy, meaning
purposefulness in name only, that is to help in our
understanding rather than to explain. See Konrad
Lorenz Introduction to Ethology.
Paul Zeldin.