Comment by tombert

Sure, I don't disagree with that. If you have a PhD in theoretical physics, you're probably in a good enough position to talk about different types of calculus, and maybe some other forms of physics depending on if there's overlap. But I think a lot of people will see "Dr." in front of the name and assume that these people are like the professor from Gilligan's Island and understand everything about everything.

It's entirely possible that a PhD theoretical physicist does know a lot about biology (maybe they got a job in a biophysics or something) but I'm saying it's definitely not implied, and it might even suggest that they don't have expertise in that field.