[FOM] FOM: The Law of Excluded Middle
corcoran at buffalo.edu
Sun Oct 16 15:28:52 EDT 2005
In the 1999 Cambridge Dictionary of Philosophy under "Laws of Thought"
we read that the expression 'Law of Excluded Middle' is ambiguous. The
article goes on to list several senses including: "Every proposition is
either true or false", "Every property either belongs or does not belong
to a given entity", "Given any proposition, either it or its negation is
true". The author explicitly disclaims giving an exhaustive list. I can
think of others myself including several that are obviously false:
"Every proposition is either known to be true or known to be false",
"Every property is either known to belong or known not belong to a given
entity", "Given any proposition, either it or its negation is known to
be true". Just starting here, given the notorious ambiguity of 'or',
'not', 'proposition' and 'known', we have an impressive array of choices
to work though.
Q1 Is there any generally accepted meaning of 'the law of excluded
middle' or related expression as it occurs in foundational debates?
Q2 Does any of the contributors to the FOM exchange have a specific
preferred sense for 'the law of excluded middle' or related expression
as it occurs in foundational debates?
Q3 Is there a place in the literature that discusses the range of
meanings that this expression has been made to carry over its long
Q4. Do all of the contributors agree as to what this law is about:
strings of characters, people's thoughts, people's assertions, abstract
propositions in the sense of Alonzo Church 1956, "meaningful sentences"
in the sense of Tarski 1956 or something else?
Q5 Has any contributor to this debate prefaced his or her contribution
with remarks sufficient to clarify the intended meaning of this
More information about the FOM