Speaking as a PhD student, I think everyone having a PhD would be an extreme net negative on society -- even putting aside questions of opportunity cost or social signaling. PhD study hyper-specializes people, which is important for getting some scientific progress done, but I think it would make it more difficult for people to relate to each other and make valuable broad-minded connections outside of their field.
But I do think that the social signalling aspect is the dominant factor for most people's decision to get higher education. Imagine a world in which it was mandated that degrees were not allowed to be made public, to employers or anyone, and the presence or absence of a formal degree was not allowed to be a deciding factor in employment. Employers would likely find informal proxies to test for skills (either basic competence or specialized knowledge). Would-be students probably wouldn't go to college. And there's nothing wrong with that, because most jobs -- and most people's lives -- don't need the kind of degreed education that colleges are providing.
I would strongly disagree. A PhD dissertation itself requires a hyper-specialisation (that's the point), but doesn't mean that a person holding a PhD forever writes about the same topic.
If the world is becoming more complex as time marches onward, which I think we all think it is, then we should expect people to specialize and then hyper-specialize with more time. I'm sure most grad students have seen this illustration: http://matt.might.net/articles/phd-school-in-pictures/
It's an informative idea, that the PhD takes a lot of effort and accounts for not so much. However, it's uninformative in the representation of science being a circle or any other uniform mass. I know I'm nitpicking a quick drawing, but I see this illustration all the time in PhD-land and it makes me a bit frustrated.
The circle misinforms the reader that at large scales, the sum of human knowledge is countable, known to all, and accessible. But even more pernicious is the idea that, in the local area, where that zit on the face of science lies, the field is moving outward/progressing uniformly. That there are no holes, or that if there are, they can be seen and worked towards.
The boundary of science that a PhD pushes outward is a fractal portion of some previous portion. The circumference is always increasing and may do so until infinity, though the surface area is finite (like Euler's horn). Your doctoral work is just making more questions to be asked, though in a smaller and smaller way, like a fractal zoom. As the timestamps count up, the fractals increase in complexity, the questions science creates increase.
But it's not just science, as if 'science' can be locked away from the rest of humanity and just doled out like a communion wafer. Science is human, all of us (eventually) share in it's flowers and thorns. That includes the general populace. They are part of that fractal too. So i think that in fact, yes, given enough time, most folks will be a the level of specialization of today's PhD, because the world and the science will need for them to be there because it will be so advanced and difficult.
I'm not sure about that. By way of anecdata, there are several PhDs at my workplace, myself included. The PhDs are the most likely to be doing multi-disciplinary work, and to quickly move into new areas.
At least by tradition, the doctoral education was supposed to be about "learning how to learn," and though the research topic was specialized, you had to pick up a lot of breadth in order to make it work. In my case, though I studied some arcane properties of atoms, in order to conduct my project, I had to learn electronics, programming, and a variety of other things.
Now, another thing about the PhD education is that no two PhDs are alike, which makes it hard to talk about having a PhD as a sort of symbol -- of what? Take two PhDs in nearly the same area, and they will have remarkably different sets of knowledge and approaches to problems. A PhD project is a series of disasters, not a smooth trajectory towards mastery of a narrow field.
And as you move up the academic ladder, you are given more freedom to forge your own education, including an education that makes you more employable, or less so. Perhaps how you get yourself through your PhD amplifies the small things that make you unique as a person and problem solver.
(Note that there's some hidden advice here. If the degree itself won't make you desirable, you have to make yourself desirable by what you add to your abilities).
I believe a proper PhD education should allow one to dig into any subjects given enough time and examine them in great depth. It would help greatly in spotting misdirections and fallacies even in published research. Most of the PhDs I know are quite open to be convinced by sound reasoning even though they might disagree at first, and that is a great boon to societal decision making.
The issues of costs, ROI, and capabilities/interests do make it difficult to push everyone toward getting a PhD though.
> Most of the PhDs I know are quite open to be convinced by sound reasoning even though they might disagree at first, and that is a great boon to societal decision making.
Correlation is not causation. A potentially more likely explanation is that people more open to changing their mind are more likely to be willing and able to get a PhD.
But I do think that the social signalling aspect is the dominant factor for most people's decision to get higher education. Imagine a world in which it was mandated that degrees were not allowed to be made public, to employers or anyone, and the presence or absence of a formal degree was not allowed to be a deciding factor in employment. Employers would likely find informal proxies to test for skills (either basic competence or specialized knowledge). Would-be students probably wouldn't go to college. And there's nothing wrong with that, because most jobs -- and most people's lives -- don't need the kind of degreed education that colleges are providing.