I am curious to know whether PhD is the highest degree one can earn? Is there any other degree beyond that, if so what is it and what are the universities offering the same?
In Finland, someone with a doctor's degree and additional body of scientific work equivalent to another thesis can apply for the title of docent (dosentti). The title gives the right to mentor PhD students. Docenture is a degree in the sense that it does not imply employment at the university which bestows the title.
At least some professors consider it kind of a vestige and it might be phased out at some point.