This is one of those posts on a somewhat abstract topic that I’m putting here for later so that I can point at the post and say “I mean that”.
This blog is interested in both logic and fiction. That is a problematic combination because you would assume logic is about objective truth and the qualities of fiction are subjective.
Objective truths pertain to things whose truth (in theory) is independent of any one person. There are issues with that but for the sake of argument let’s assume that we all know what we mean. If I say that a given novel was written in English, I am making a claim about an apparently objective truth. It isn’t enough to say that it is my opinion.
Subjective truths pertain to things whose truth rest with one person’s feelings and thoughts. I can know when I’m bored by a book but it is a subjective truth that the book is boring.
The gulf isn’t unsurmountable. Feelings and mental states can be observed in various ways and with the right experimental design I can establish truths that are objective but rest on subjective experiences. For example a claim that 90% of a given set of people find a book boring is a claim about an objective truth that can be investigated empirically.
Intersubjectivity is something else. Intersubjective truths rest on agreements between people. They behave in some ways like objective truths but at the same time they seem to rest on quite arbitrary grounds. The most obvious example is the meaning of words.
Words do not gain their meaning from some objective physical properties. The etymology of words might suggest meanings but there is no guarantee that the meaning of the word can be found from looking at it parts. If you find that hard to understand then just consider the word ‘understand’.
So while it seems like you could just pick any arbitrary meaning for a word and change how you would like, in reality you can’t because a word is only useful if other people know what you mean by it.
Intersubjective truths can feel a little baffling – they aren’t necessarily the same as a generally held opinion but they don’t seem to have anything thing else very much underneath them. And many important things like morality, social conduct, word meanings and grammar may rest on this notion of intersubjectivity.