Why are PhDs the most common doctoral degree?
This answer suffered a Major Revision!
A Ph.D. is an academic doctoral degree and have nothing to do with philosophy nowadays.
From Wikipedia:
In the context of the Doctor of Philosophy and other similarly titled degrees, the term "philosophy" does not refer to the field or academic discipline of philosophy, but is used in a broader sense in accordance with its original Greek meaning, which is "love of wisdom".
People often refers to an academic doctorate as a Ph.D., even when the official title in their university/country is different of Doctor of Philosophy. The reason beyond its popularity is because a Ph.D. is a title traditionally conceded in countries with anglo-saxonic language and since the common language in the academia is English we often "translate" our titles to the equivalent in English.
I have recently learned with @Pete L. Clark that there are different types of doctorates in the US that give the same legal statute as an academic doctorate, but with different structure and requisites from a doctorate in Science. The example that he used was the Doctor of Arts (D.A.), a title that gives equivalent rights as a Ph.D. in which concerns teaching and research in universities.
My previous misunderstanding was due to the structure of high level education that I am used to in Portugal and Brazil. In both countries Therapists, Physicians, Lawyers and others do not have a doctoral degree. In Portugal a physician have Master's degree in Health Science or a 6 years pre-bologna licenciatura degree (undergraduate degree). If a physician/lawyer/therapists wants to have a doctoral degree here they need to engage in a minimum 3 years doctoral course, publish articles and defend an original thesis.
For a historical insight and more complete overview, please read this article and this article.
I'm sorry for the previous wrong answer. I think the question is too wide and depends highly on which country we are talking about. I assumed things about the doctoral degrees on the US that are not true.
Edit: Of course that there are many different ways to refer to an academic doctorate depending on the country the title is emitted. The point is: they are all equivalent. A German Doktorgrad is equivalent to a Ph.D. in the UK and to a Doutoramento/Doutorado in Portugal/Brazil, etc. In the other way researchers would not be able to work across the borders.
PhDs are more common because PhDs come from all fields and most countries. To talk in broad strokes (I suggest looking into each of these points, e.g. in wikipedia for more details.)
Lets break our doctorates into 3 kinds:
Research Doctorates
These are given for doing research, and intended to train researchers.
- Doctorate of Philosophy (PhD)
- all fields of study, in all countries
- Doctorate of ___ field
- Some countries: Austria, Germany, Switzerland and others
- Dr-Ing (engineering) etc
Higher doctorates
Doctor of Letters (Arts, Humanitites), Doctor of Science etc
- Field specific doctorate
- more or less lifetime achievement awards for research.
- Generally pre-req'd on having a PhD for at least 10 years.
Dr. habil
- see Habilitation
- Most common (but not restricted to) in Germany, Austria, Swizerland.
- Requires a PhD equivalent
Obviously there will be less people with any given higher doctorate than PhDs since they are a subset of people who have PhDs with in a given field.
Professional Doctorates
These are doctoral degrees that are required to do a profession.
- Medicine Doctor (MD) i.e. a Doctor of Medicine
- Every "doctor" in a hospital has at least this.
- Juris Doctor (JD) i,e Doctor of Jurisprudence
- which in many countries required to be a lawyer
- by tradition laywers never take the title Dr.
There are a lot of professional doctorate holders. You've probably seen the thing about PhD holders not using the title Dr on plane tickets because they don't want to be called upon for medical assistance (which they can not provide).
There are probably more PhDs awarded each year than MDs. But not by a huge margin.
In 2014 the US had 18,078 MDs graduate (source) and 54,070 PhDs; of those only about 40,000 were in science and engineering and of those only a very small portion would be in medical science (source).
Also in 2014 the US had 43,832 JDs graduate (source). This is as compared to only 14,000 nonscience and engineering PhDs; of which only a small portion of which would be in Law.
I posit that for any field with a professional doctorate (I can only think of MD and JD) there will be an order of magnitude more professional doctorates than PhDs in that field.
The only reason PhD numbers are so high vs professional doctorates, is because they are the same degree no matter the field.
Similarly, the only reason they are high compared to Dr.Ing etc is that those degree are only common in certain countries; and are field specific.
And vs Higher doctorates: they are prerequed on PhD, and are field specific.
In one's early education, especially in more traditional contexts, learning involved X being true because the teacher said so. Don't question the teacher; just make sure that you know X. It was all about memorization (rote learning).
This would start to change when a student would reach the highest levels of education, at which point they'd be able to argue and contribute their own understanding. So instead of focusing on rote learning, a student would have to demonstrate their ability to think and engage in critique of their field (scholasticism). This is, successful students would become philosophers of their field rather than simple repositories of memorized facts.
Education's become increasingly liberal with a shift from rote learning toward critical thinking, but there's still a semblance of that early expectation that pre-Ph.D. students are supposed to memorize what's being taught while a Ph.D. would symbolize one's ability to go beyond that.
Historical background
Academics used to be folks who participated in medieval universities. There was a heavy religious flavoring to academia compared to today's more secular settings, but it was still general academia nonetheless.
A lot of stuff came from this time. For example, on graduation when you dress up like Harry Potter, it's because that's how these guys used to dress.
Anyway, so this is where the Bachelor's/Master's/doctorate thing came from:
Course of study
University studies took six years for a Master of Arts degree (a Bachelor of Arts degree was awarded after completing the third or fourth year). Studies for this were organized by the faculty of arts, where the seven liberal arts were taught: arithmetic, geometry, astronomy, music theory, grammar, logic, and rhetoric. All instruction was given in Latin and students were expected to converse in that language. The trivium comprised the three subjects that were taught first: grammar, logic, and rhetoric. These three subjects were the most important of the seven liberal arts for medieval students. The curriculum came also to include the three Aristotelian philosophies: physics, metaphysics and moral philosophy.
-"Medieval university", Wikpiedia [links and citations omitted]
And that stuff was a lot of the rote learning, before one was a proper doctor.
After that, one'd go into the realm of philosophy, becoming a more critical thinker (scholar):
Once a Master of Arts degree had been conferred, the student could leave the university or pursue further studies in one of the higher faculties, law, medicine, or theology, the last one being the most prestigious. A popular textbook for theological study was called the Sentences (Quattuor libri sententiarum) of Peter Lombard; theology students as well as masters were required to write extensive commentaries on this text as part of their curriculum.[citation needed] Studies in the higher faculties could take up to twelve years for a master's degree or doctorate (initially the two were synonymous), though again a bachelor's and a licentiate's degree could be awarded along the way.
-"Medieval university", Wikpiedia [links and citations omitted]
This system was already established by the time "science" started to be recognized in a more modern sense. At that time, it was still just Philosophy, or more specifically "Natural Philosophy".
So, to be a "doctor of philosophy" is literally just that - to be a scholar of philosophy who's gone beyond the intro years of rote memorization to the point where they can engage in scholarly critique of their field.
Ph.D.'s as further Master's degrees
In the historical context in which these degrees were named, the human knowledge pool was way, way smaller. It was a drop compared to today's oceans. And so, the prospect of learning much of the human knowledge pool was far more reasonable, if many'd still have regarded it as challenging.
Today, a lot of Ph.D.'s are awarded to students who probably don't quite get the whole philosophy-of-their-field thing. That seems to be a natural consequence of there being a lot more one can learn before reaching the point of critique and abstraction.
So, today, a Ph.D. can be something like a fancy Master's degree. For example, one can basically get a Master's in Chemistry, then do a bunch of lab work to test something out, and get a Ph.D. for that (experimental chemistry).
In principle, we might argue that there's some need for revision to the academic credentialing system to better capture its modern reality. And we've actually kinda done that already - as noted in the Wikipedia link above, a Master's and doctorate used to be the same thing; they got more separated in part due to the human knowledge pool growing and more ranks being needed to account for it. But that'd be a different topic.
For the purposes of this question, a Ph.D. got its name in the scholarly days when academics were basically those who learned their field and then engaged in scholarly critique of it. And today, the name's kinda a historical artifact.
Further reading
I found a neat paper that discusses the evolution of doctoral conference since the scholarly days:
- "Hora Est!: On Dissertations", 2005.
This document's a look at what scholastics/academics had to do to be recognized as a doctor. And while the title specifies "On Dissertations", it notes:
Less than a century ago a dissertation was not always required to obtain a doctorate. Successfully defending a number of theses sufficed. [-page 7]
Other interesting factoids:
Apparently dissertations used to be more about disputing (critique) points, written up as a disputation. This contrasts with the modern description of a PhD being about adding to the human knowledge pool.
It seems like prior academia was far more concerned with religion than modern academia. Early academics seem to have been something like clergy.