Using Instance Variables in a Class?

The way that it read in the book, and i'm wondering if i read it somewhat wrong, is methods should affect as many of these variables in the class as possible. Wrote, if you have a method that's only touching a single then why is it an instance? Why not just make it in line to the er? You bring it into that um method? Right? So that that was interesting. And what i really loved about this thor is i got my it got me thinking about em I wonder if there's some tools out there, whether it be a static code of analysis type of tool, or a tool that could run in real time,. That could measure a the cohesion