Someone might *theoretically* consider this in highly specific, unusual circumstances, such as:
* Highly overlapping research areas: If the two PhDs are in very closely related fields (e.g., one in bioinformatics and one in computational biology), *some* coursework and research might be partially transferable. However, even then, the administrative burden and sheer volume of work would still be staggering. It's far more efficient to design a single, interdisciplinary PhD program.
* Exceptional circumstances: Perhaps an individual has already completed almost all the requirements for one PhD and simultaneously undertakes another highly complementary PhD, but this scenario is highly unlikely and still carries significant risk.
However, the significant drawbacks far outweigh any potential "benefits":
* Immense workload: The sheer volume of research, coursework, and examinations would be overwhelming, leading to burnout, poor mental health, and potentially failed dissertations.
* Prolonged timeframe: Instead of finishing one PhD in a reasonable timeframe, the individual is likely to take much longer to complete both, leading to lost opportunities (postdoctoral positions, career advancements).
* Funding challenges: Securing funding for two PhD programs simultaneously is incredibly difficult.
* Lack of focus: Trying to juggle two distinct research projects can result in diluted effort and lower quality work on both.
* Administrative hurdles: Coordinating between two different universities and departments would be complex and time-consuming.
* Missed opportunities: The time spent on two PhDs could be better spent focusing on one and then pursuing a postdoctoral position in a related field.
In short, pursuing two PhDs simultaneously is almost always a bad idea. It's a high-risk, low-reward strategy that's likely to lead to significant stress, delays, and ultimately, less successful outcomes than pursuing a single, well-focused PhD. A much better strategy would be to carefully plan a single, potentially interdisciplinary PhD that encompasses the desired knowledge and skills.