I never quite understood why you need to do a postdoc after completing your PhD. Is it like getting an unofficial second PhD?
No, it's not like a second PhD, because there's little to no documented requirements, no thesis, no defense, no coursework, etc.
In the 'old days' (prior to the squeeze on academic funding and exponential increase in PhD candidates), one took a post doc primarily to:
- Learn a new skill, technique, or method
- Dedicate a few years time conducting research to strengthen one's CV without the added stress of teaching and other tenure-track requirements.
Ideally, the post doc came out a very desirable candidate armed with a great research program and toolbox.
Today, a post doc is quickly becoming mandatory for academic-track scientists, as the pool of jobs shrink and the pool of candidates expand. It is not uncommon to find people doing multiple post docs, or people finding themselves in a permanent post doc (or research scientist) position.
While this is somewhat discouraging, the simple fact that funding is scarce and science can be expensive suggests that the ideal candidate has a proven track record and is likely to secure additional grants. Post docs provide one the time and resources to prove that tangibly.
Why do you need to do a postdoc after getting your PhD?
In practice? Because very likely you won't be able to get any better (academic) job than that.
These days "postdoc" simply means a research position that is not permanent or indefinite (e.g. tenure track). It is far, far easier to land (yet another) postdoc than a permanent position.
This applies to the fields I'm familiar with (mostly sciences). The humanities may be different.
It's not a second PhD, because the length of the postdoc is typically much shorter than that of a PhD.
The function of a postdoc is sort of an "advanced apprenticeship," where you may choose your advisor (who should be different from your graduate advisor!) according to several possible goals, including:
- Learning a new technique or field
- Gaining further experience in a slightly different area from your graduate research
- Personal needs (such as the "two-body" problem)
Such positions usually last anywhere from one to four years, depending on funding. Your duties will also likely involve helping to supervise some of the graduate or undergraduate students in the group. You may or may not also have some teaching duties. But you typically don't have the obligation to write grants and "bring in" money.
If you intend to work in industry, you don't need and should not do a postdoc.
If you want a job in academic, it often requires a strong profile. You need to do a postdoc to continue doing research, and building up your profile.
1. There isn't really such a thing as a "post-doc"
A "post-doc" is just a non-tenured fixed-term research position which requires the maturity and experience which a Ph.D. degree is a recognition of. That's it.
Now, it's true that it's customary to spend time in such a position, and in many academic institutions tenured position candidates are considered to be inadequate if they have not first had a stint (or two) as non-tenured "post-docs" somewhere - but there's no fundamental principle at work here.
2. Weakness of the academic staff (in terms of collective ethos, organization and action)
You could rephrase your question this way: "Why not just hire people with Ph.D.s into tenure track positions?" And indeed, there is no good reason not to (generally). Tenure track does not mean you actually have tenure immediately on employment; and even tenure is not some carte blanche to not do your job, or a guarantee to not be terminated. It should really be referred to as the "normal track" for employment of academics.
The thing is, non-tenure-track researchers are cheaper, and require less commitment. Additionally, universities and high-and-mighty PIs can cast this employment as something inherently temporary, increasing the chance that these employees not expect much to begin with - they'll just shuffle along. Thus in many countries there's a glut of post-doc positions and a dearth of proper academic staff positions.
Had there been a resistance from the tenured academic, or support by them to their non-tenured, more junior colleagues, in a demand to be moved into the tenure track / promoted to associate professors based on good performance, plus for permanent positions for research assistants where relevant - the balance of forces would change, and fewer people would spend many years moving from one post-doc to another despite being worthy of a proper position.
Of course, this requires academics to have a strong sense of what really benefits research; a memory of the history of their field going back several decades (if not a century); a sense of community or solidarity with their junior colleagues; and organs for collective action independent of university management, namely - academic staff unions. As the latter are often missing or weak, the former tend to be missing or weak as well.
First, you don't need to have a postdoc. The standard for whether or not a postdoc is necessary (and indeed how much "postdoc" is enough) varies wildly by field. This, incidentally, makes interdisciplinary hiring committees an interesting experience.
But it's not a "2nd PhD". What it's meant to accomplish is to be the transition period where you start to view yourself (and the field starts to view you) as an independent researcher. While working on your PhD, it's quite likely that one's advisor had a significant hand in formulating the question you were addressing, etc. The idea of a postdoc is that you can begin to mature as an independent scientist, potentially mentoring others, seeking funding, determining the direction of a project, etc. while still in a protected, mentored environment.
By analogy, if a PhD is learning to ride a bike with training wheels, a postdoc is taking the training wheels off, but still having a parent jogging by your side.