Hypothetically speaking you're right. You can teach yourself everything you need to know even if that means sitting down and going through MIT OCW with all the textbooks in the syllabi.
But practically speaking, in the real world we reside in, approximately no one authors peer reviewed research without at least being in graduate school. You frequently see "talks" at conferences given by non-PhDs, but it's exceptionally rare to find math or computer science research published in reputable journals or conferences by non-PhDs.
The dirty secret is that the formal barrier to entry was never really the problem. It's extraordinarily difficult to learn how to conduct meaningful research. The structure of a PhD is imperfect, but it places you in direct collaboration with an experienced researcher who can mentor you. Half of the entire work of a PhD program is precisely learning how to learn on your own so you can find interesting research questions.
I don't think it's productive to talk about what's merely possible. A more realistic barometer is what's plausible. Anyone who can bootstrap themselves up to original research in math or computer science through independent study is extremely gifted. You don't want to set a goal that requires you to be extremely gifted right from the start.
Effective research is not always published. There are volumes of private research in technical disciplines you will never hear about. There is not enough data available for you to declare confidently that the PhD is a strong requirement for real research. Furthermore, especially in the field of computer science, you should really run the numbers on how many of ex. the 10 authors on each of the 100 Google papers put out each year had a PhD.
Additionally, nothing has been done to separate the issue of correlation and causation. If research capable individuals pursue a PhD because it interests them, who's to say that their research capability came from the PhD versus it being intrinsic.
One can learn a lot from a PhD. But saying that it's a practical requirement for research in this modern era of information access is without definitive evidence.
But practically speaking, in the real world we reside in, approximately no one authors peer reviewed research without at least being in graduate school. You frequently see "talks" at conferences given by non-PhDs, but it's exceptionally rare to find math or computer science research published in reputable journals or conferences by non-PhDs.
The dirty secret is that the formal barrier to entry was never really the problem. It's extraordinarily difficult to learn how to conduct meaningful research. The structure of a PhD is imperfect, but it places you in direct collaboration with an experienced researcher who can mentor you. Half of the entire work of a PhD program is precisely learning how to learn on your own so you can find interesting research questions.
I don't think it's productive to talk about what's merely possible. A more realistic barometer is what's plausible. Anyone who can bootstrap themselves up to original research in math or computer science through independent study is extremely gifted. You don't want to set a goal that requires you to be extremely gifted right from the start.