I took an IP law class in grad school. I asked the professor a question about making a more clear rule about how much is use of a copyrighted work is fair use o

I took an IP law class in grad school. I asked the professor a question about making a more clear rule about how much is use of a copyrighted work is fair use or something along those lines. (I think I had some vague idea about using information theory to quantify it though I didn't say that.) The response was some argument against "bright-line rules" [1] like what I was proposing. I personally can see how bright-line rules can be bad in some contexts, but I don't think copyright is one of them. Legal clarity would be very helpful here in my view. [1] https://en.wikipedia.org/wiki/Bright-line_rule https://en.wikipedia.org/wiki/Bright-line_rule