Vagrant predicates are logical constructions that exhibit an inherent limit to conceptual knowledge.
Such predicates can be used in general descriptions but are self-contradictory when applied to particulars. For instance, there are numbers which have never been mentioned but no example can be given as this would contradict its definition. Vagrant predicates have been proposed and studied by
Nicholas Rescher
Nicholas Rescher (; ; born 15 July 1928) is a German-American philosopher, polymath, and author, who has been a professor of philosophy at the University of Pittsburgh since 1961. He is chairman of the Center for Philosophy of Science and was fo ...
.
F is a vagrant predicate
iff
In logic and related fields such as mathematics and philosophy, "if and only if" (shortened as "iff") is a biconditional logical connective between statements, where either both statements are true or both are false.
The connective is bicon ...
(
u)Fu is true while nevertheless Fu
0 is false for each and every specifically identified u
0.
When
infinity
Infinity is that which is boundless, endless, or larger than any natural number. It is often denoted by the infinity symbol .
Since the time of the ancient Greeks, the philosophical nature of infinity was the subject of many discussions amo ...
is thought of as a number greater than any given, a similar idea is conceived. However vagrancy needs not to be monotonous and occurs also within bounds. Rescher has used vagrant predicates to solve the
vagueness
In linguistics and philosophy, a vague predicate is one which gives rise to borderline cases. For example, the English adjective "tall" is vague since it is not clearly true or false for someone of middling height. By contrast, the word "prime" is ...
problem.
[
]
References
Logic
{{logic-stub