A while ago I had a conversation with a colleague, that went something like this:
Me: “I’ve come across a new book that would be really useful to you for the module you’re teaching next term.”
Colleague: “I don’t really think I need that.”
Me: “No, it’s really good, you will find it really useful.”
Colleague (rather angry): “I appreciate your suggestions, but I REALLY DON’T NEED A BOOK ON THE SUBJECT.”
It eventually transpired that my colleague was interpreting “you will find this book useful” as “Because you don’t know the subject of the course very well, you will need a book to help you learn the subject before you teach it to the students.”. By contrast, I was meaning “you will find it useful as a book to recommend to your students“.
This subtle elision between “you” being taken literally and being used in a slightly elided way to mean “something you are responsible for” is easily misunderstood. Another example that comes up frequently is when I am discussing with students some work that they have to do on a project. I will say something like “you need to make an index of the terms in the set of documents”, using the common elision in software development of “you need to” to mean “you need to write code to”, not “you need to do this by hand”. Most of the time the students get this, but on a significant minority of occasions there is a look of incomprehension on the student’s faces as they think I have asked them to do the whole damn tedious thing by themselves.