People with multiple PhDs and People teach in different departments Is it allowed for people to obtain multiple PhDs at different stages of their career? I am thinking of Phys and Bio.
Then regardless of that, is it allowed to teach in different departments at one or multiple institutions. (But I would want a tenured-position somewhere.) By teaching, I also wish to include doing relevant research in the two different fields. (for me, maybe physics and biology. Beware: Not biophys.)

John
There is, in general, no prohibition on getting multiple PhDs.* However, it is usually not recommended. This topic is covered in another questions on this site, e.g., When does one go for a double doctorate?

Teaching in multiple departments at a university is unrelated to having multiple PhDs. Usually someone who teaches in two departments effectively teaches "one thing" that is relevant to both departments, rather than teaching two unrelated things. For example, someone who specializes in internet law is likely to be associated with both the law and computer science departments.

*Although some universities/departments won't let you join their PhD program if you already have a PhD