MHB Can Predicate Properties Be Neither True nor False?

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The discussion centers on the nature of predicates in logic, specifically whether they can be neither true nor false. It is established that a predicate is defined as a function from a set \(X\) to \(\{\text{true}, \text{false}\}\), indicating that predicates inherently yield binary truth values. The participants agree that while the truth set of a predicate can be empty, the notion of a predicate containing variables requires clearer definitions. The conclusion emphasizes the importance of precise language when discussing logical predicates.

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  • Understanding of logical predicates and their definitions
  • Familiarity with truth sets in mathematical logic
  • Basic knowledge of functions and their properties
  • Awareness of logical terminology, such as "true" and "false"
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I'm not very sure whether a predicate can be neither true or false, and I haven't seen any example so far.

The second choice is false because it is the truth set that is the set of all values which make the predicate true.
A predicate has finite variables, so the third choice is false too.

I believe the truth set of a predicate can be empty, so the last choice is true.
 
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I agree with your choices, but I find the questions not precise enough. According to Wikipedia, a predicate on a set $X$ is a function from $X$ to $\{\text{true}, \text{false}\}$. With this definition it is not clear what "always" means in question 1 and what it means for a predicate to contain variables in question 3.
 
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