I just started a 3 year Post-Doc position at an engineering department at an German University. The Professor here, informally asked about my ambitions to do a Habilitation. I know that is the common route at least in several European countries in the direction of a permanent faculty position. However the planned activities, and research topics for the Post-Doc also seem suitable to do a second PhD in computer Science (while my current PhD is in Mechanical Engineering). Of course I would have to be an external advisor from the CS department, but i think that is manageable, since i already have some publications in the field of one of their groups and some positive informal contact to one of the Professors there. Also i feel confident that i wont need to much of their time for guidance since i already have the experience of the first PhD. My reasons to be more inclined towards a second PhD. instead of a Habilitation are that i think i will get bored of my current field in a couple of years, and the second PhD seems to give e a better chance to change fields later. On the other hand i do not know any people who did something like that. And i can not really predict the consequences or reaction of such a unconventional route. And i also do not want to freak out my new boss by mentioning this idea, if the majority of you would consider it as very inappropriate. What are the pros and cons of extending your research field by doing a second PhD in another direction stead of deepening while doing a Habilitation in the same field? Are there any big disadvantages for the Professor of the department which employs me which i maybe overlooked? EDIT: The current Position is in Germany. Although i would be interested in staying in Germany, i would also like to hear about perspectives on this for other countries. That also makes the value of the question more general.