Are Propositions the (Only) Bearers of Truth?
Many logic textbooks include a definition of “proposition” close to the beginning that goes something like this:
A proposition is the content or meaning of a declarative sentence in ordinary language. Propositions are is truth evaluable, which means they can be assigned truth values such as True and False.
The idea is that a proposition is the underlying meaning of whatever bits of language we use to make assertions about the way things are. As bits of language, they can be evaluated and since they are about the way things are, they can be evaluated for their resemblance to the way things actually are. If someone says things are one way but things aren’t that way, then we can evaluate that person’s saying so as bad or wrong or infelicitous or false.
But language is complicated and we don’t only make assertions with words. We also make prescriptions, requests, demands, inquisitions, permissions, forbiddings, warnings, acknowledgements, hypotheticals, and so on. We also use things that aren’t words to describe the way things are, like pictures, charts, patterns, emoji, scale models, colors, and tones.
Since propositions are truth evaluable, they can be given a logic. In fact, most logics are about propositions. But using “logic” this way is a pretty low bar, since here all I mean is that given a system of objects and a consistent evaluative frame over those objects, you can give a logic over those objects. Most logics are just evaluating the relations between propositions and their standard evaluative frame, which is truth.
This raises two questions: first, are other linguistic objects truth evaluable, evaluable in some other way, or not evaluable whatsoever? Second, if they are evaluable what does a logic of these linguistic objects look like?
If other linguistic objects like prescriptions and queries are truth evaluable, then it would make sense to ask of a question like, “What time is it?” or a command like “Walk with me.” whether that question or command is true, false, or something like that. I’m not sure the it does make sense to ask whether these things are true, although there is something evaluable about both questions and commands.
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