In the context of academic degrees, the term "philosophy" does not refer solely to the field of philosophy, but is used in a broader sense in accordance with its original Greek meaning, which is "love of wisdom". Wikipedia

That is the sense in which the Ph D degrees in any discipline are considered as getting deeper into the knowledge level of the subject..

http://en.wikipedia.org/wiki/Doctor_of_Philosophy

Dear @Reginald, there is no Ph.D in Mathematics; it is usually in Philosophy. This makes sense because Mathematics is built on logical and Philosophical bases. The other Ph. D in Science is for farther distinguished achievements.

My PhD is a Dr. rer. nat.

I´m physicist.

The PhD is a doctoral degree,The PhD title is misleading because PhD holders are not necessarily philosophers (unless they earned their degree in philosophy!). PhD recipients are able to engage in thought experiments, reason about problems, and solve problems in sophisticated ways.

In the context of academic degrees, the term "philosophy" does not refer solely to the field of philosophy, but is used in a broader sense in accordance with its original Greek meaning, which is "love of wisdom".

http://www.phdstudies.com/PhD/Economics/Distance-learning/

In the context of academic degrees, the term "philosophy" does not refer solely to the field of philosophy, but is used in a broader sense in accordance with its original Greek meaning, which is "love of wisdom". Wikipedia

That is the sense in which the Ph D degrees in any discipline are considered as getting deeper into the knowledge level of the subject..

http://en.wikipedia.org/wiki/Doctor_of_Philosophy

My Ph.D. was conferred for pursuing studies in Hispanic language and literature. However, a brief glance at my curriculum vitae will show that I preferentially studied 20th century Spanish philosophers (esp. Ortega y Gasset, Unamuno, Zubiri, Laín Entralgo and German philosopher Hermann Cohen, on whom I wrote a book).  I did deal with epistemology (and many other disciplines customarily classified under philosophy).  Therefore the "Philosophiae" in my "Philosophiae Doctor" degree was truly meaningful. This did not prevent me from researching other Hispanic disciplines, like musicology and literature. More accurate would have been a degree title, "Culturae Doctor."

Dear @Reginald, very good explanation of Ph.D degree  along with descriptions, subjects areas, schools in US is attached. History, English, Engineering, Philosophy and Economics are some of subjects areas!

http://education-portal.com/articles/What_Does_PhD_Stand_For.html

Dear Ljubomir, Thank you for the link you have provided. It is really a valuable source.

It is difficult to draw a line between philosophy and PhD. As explained well by respected @Dr. Rao, philosophy in a broader sense. Moreover, Doctor of  Philosophy for PhD is being used as a conventional name.

Here is a good explanation of a what a Ph D actually stands for in terms of knowledge. Also read the comments.

A book for Ph D students and supervisors.

http://gizmodo.com/5613794/what-is-exactly-a-doctorate

http://www.amazon.co.uk/gp/product/0335242022?ie=UTF8&tag=findaphdcom-21&linkCode=as2&camp=1634&creative=6738&creativeASIN=0335242022

This is just a tribute to an old standard indeed with rare occasions of somebody wondering what does it actually mean. In the same way, one may say that a title "doctor" has nothing to do with M.D. and recall a joke about it:

"An announcement from a cockpit:  - We have a medical emergency. Do we have a REAL doctor on a plane?"

Dear All,

PhD = philosophiae doctor (doctor of philosophy)

The medieval university made possible the study of arts, law, medicine and theology.

Philosophy was only an introductory study for theology. „Philosophia est ancilla theologiae.” The degree of philosophiae doctor was developed in Germany in the 18th- and 19th-centuries and now it is acknowledged all over the world.

Scientists were often distinguished philosophers like Aristotle, Plato, Avicenna, Francis Bacon, René Descartes, David Hume, Gottfried Wilhelm Leibnitz.

Philosophers studied and formulated ethics, logic, metaphysics which play a central role in scientific theories and methodology. Philosophy has been always attached to the theoretical solving of humanistic and general troubles during the history of mankind.

Can one say scientia est ancilla philosophiae or philosophia est ancilla scientiae?

These days some scientists work on tiny scientific fields and are specialists of micro areas. Are they able to see the whole field or determining parts of human needs? Or are they able to contribute to the true human welfare?

Here you can find some ideas on the philosophy PhD degree connection:

https://www.researchgate.net/post/Is_a_PhD_a_PhD?_tpcectx=profile_questions

That is very true dear @Serge. Have You ever been treated by someone as MD because You are Doctor of science in Physics? Only medicine counts! :) 

It is funny, I have been treated as a (M)Doctor! I experienced that my friend whom I have not seen for more than 20 years was seeking prescription drugs from me! Very true and very funny!

I am in concurrence with N.Rao and as you progress in your studies your wisdom gets better.

Dear @Andras, thanks for very fine thread indeed with many good responses!

Dear All,

Hanno’s degree is Doctor rerum naturalium - Doctor of natural sciences = all natural sciences including mathematics and physics.

Dear All,

My original degree is candidate of sciences (Candidatus scientarum = CSc., since 1994 replaced by common PhD.) It was granted by the Hungarian Academy of Sciences. This is a Soviet type scientific degree because this was compulsory in the socialism.

Dear Ljubomir,

What about in Yugoslavia?

Dear All,

I can row together with Nelson because one of my minor subjects in the doctoral examinations was general philosophy and dialectic materialism.

Dear Abdella,

My highest mathematics degree says "Doctor of Philosophy " which is commonly abbreviated by Ph.D. or PhD and true with most mathematics professors who have that degree use PhD in their names. However, as others indicated, the mere reason the term is used to simply describe what is called "love of wisdom" (literal meaning of philosophy from Greek term)  - a virtue of a person of high intellect to think, imagine, search and utilize the highest level of knowledge to justify and validate truth in that particular field. 

Dear @Hanno, My PhD is a Dr. rer. nat.

I´m Mathematician. I wonder what does it refer to?

Dear Serge,

The word doctor is derived from doceo, docere that is to teach thus a doctor is a teacher and not a healer.

So there are here many doctors!

Dr. rer. nat. stands for doctor rerum naturalium (German Doctor's degree in natural sciences), see the link:

http://www.acronymfinder.com/doctor-rerum-naturalium-%28German-Doctor%27s-degree-in-natural-sciences%29e%29-%28Dr.-rer.-nat.%29.html

Why not doctor in Mathematics or Doctor in a sub-discipline of Mathematics?

Why not Doctor in Ornithology or a sub-discipline in Ornithology

Etc...

Dear Abedallah,

Where have you got your degree?

In the former USSR and current Russia (and I believe in some other countries), there are TWO levels of the so-called "doctorate" degrees. The first one is equivalent to Ph.D. and it literally means " a candidate of technical sciences" or "a candidate of physical and mathematical sciences" depending on a area of concentration. The second one is awarded for substantial contributions (after Ph.D. level) and is called " a Doctor of Science", D.Sc.  

http://en.wikipedia.org/wiki/Doctor_of_Science

Yes indeed dear @Dejenie, "the highest mathematics degree is "Doctor of Philosophy " which is commonly abbreviated by Ph.D. or PhD and true with most mathematics professors who have that degree use PhD in their names. However, as others indicated, the mere reason the term is used to simply describe what is called "love of wisdom" (literal meaning of philosophy from Greek term) - a virtue of a person of high intellect to think, imagine, search and utilize the highest level of knowledge to justify and validate truth in that particular field."

Mathematics is not a special case for being in "love with wisdom", but Mathematics was developed on Philosophy ideas at the beginning.

Dear @András, I  got my degree from West Germany.

Dear @Marcel, I think the universities do follow traditional names for the degrees and usually do not prefer to change it. Like you, I prefer to have degrees in the specific field: doctor in Mathematics or Doctor in  Ornithology and so on.

Dear Serge,

Not only in the Soviet Union but also in the East-and Central European countries – except GDR (German Democratic Republic) the soviet type degrees were obligatory. My original degree is candidate of sciences (Candidatus scientarum = CSc., since 1994 replaced by common PhD.) It was granted by the Hungarian Academy of Sciences. The second degree was the DSc (Doctor of Sciences). I note intensive political activity e.g. being secretary of the communist party was a big advantage to get a scientific degree – the Orwellian rule worked...

Dear Abedallah,

Dass heisst, Sie müssen gut Deutsch sprechen? Nicht wahr?

I don't think the title of doctor of philosophy is historic. I think it is the right title, whatever the subject. To earn a PhD it matters virtually nothing what subject you have studied. Many go on to other fields or leave the sterile ivory towers of academia to pursue learning elsewhere. The title of PhD should, as in the past, simply indicate that an individual has spent enough time learning, and particularly learning by his or her own mistakes and initiatives, to begin to teach others. Philosophy is just that - a level of learning that is deep enough to be able to teach others. And since academic philosophy itself, as a discipline, has largely lost its way there is far more philosophy to be found in discussion with an ornithologist like Marcel than in a philosophy tutorial room - I know from experience of both! 

That sounds very like an academic philosophical answer, Mark!!!

In keeping with the original meaning of the term philosophy, love of wisdom, Ph.D recipients meant to be experts in wisdom and they are able to engage in thought experiments, reason about problems, and solve problems in sophisticated ways.

The title is perhaps misleading and could be changed to Dr of Science or Dr of Engineering like it is the case for corresponding master's degrees.

Ph.D, Doesn't mean you are specialist in philosophy. It means you are a philosopher in your field of study, and you've reached the theoretical basis in a particular branch.

The definition of philosophy in Oxford dictionary

The study of the theoretical basis of a particular branch of knowledge or experience: "the philosophy of science"

May I experience, why the clear definition of PhD is such a problem?

I´ve no problems to discuss with PhDs, Dr. rer. nats, DScs or some other interesting labels. The most important criterion for dialogue partners is the scientific and intelligent behaviour.

P in PhD does correspond to the study of Philosophy.

Agree with @Hanno, titles does not matter, its the attitude and action towards research that to be counted upon.

Aber sicher lieber @András. Ich habe Duetsch gelernt und gelert.

Doctor of Science degree is earned with the approval of a committee on the basis of original research and publications, and it is awarded predominantly in doctoral-level science programs, such as engineering. The D. Sc. degree is considered at a higher status than PhD.

http://en.wikipedia.org/wiki/Doctor_of_Science

http://www3.imperial.ac.uk/registry/currentstudents/dsc

For many eons, the term philosophy has been used to describe the knowledge spectrurm, from the arts, literature, science and mathematics.   After all, most of us who have earned a Ph.D. view ourselves as scholars and caretakers of some form of specialized knowledge considered within the spectrum of Philosophy.   So I suggest that the umbrella term Doctor of Philosophy be retained.   Anything else suggests a narrowing of the scope (and depth) of our knowledge.

Dear James,

You are right with your historical interpretation and presentation. But your suggested narrowing of my scope and knowledge because of the non-PhD?

I don´t believe it.

PhD degree is an abbreviation for the top level degree, just like MPhil, Msc, Bsc... and other lower degrees.

If the holder is a Philosopher, then this is another story and has nothing to do with the title.

Dear @Andras, I have god my Dr Sci of Technical Sciences  from the  University of Belgrade in 1985, in the field of Automation and Control!

In most of Europe, all fields other than theology, law, and medicine were traditionally known as philosophy, and in Germany and elsewhere in Europe the basic faculty of (liberal) arts was known as the faculty of philosophy (Wikipedia).

Dear Mahfuz,

In keeping with your observations about liberal arts faculties in Europe, one can also observe that in the past a Ph.D. had its roots in a liberal arts education.   So, it was common for most faculties to award Ph.D.s.    But then other forms of degrees began to appear.   In my faculty which is an engineering faculty, for example, we award both the Ph.D. for research oriented tracts and Master of Engineering for project-oriented tracts.    The unfortunate part of this diverging away from the liberal arts is that it is possible to graduate with a Ph.D. without ever having taken a Philosophy or Language or History or Literature course.

All PhD degrees are Philosophy degrees, philosophy can be in any discipline, ideas and thoughts implemented throughout all fields and expertise.   

@Kuldeep Dhama: All PhD degrees are Philosophy degrees...

I did a little digging in terms of the history of Ph.D. (doctorate) and found that this history reaches back to the Middle Ages.   In Europe in the  1200s, a doctorate was a form of license to teach Latin.    A very detailed history of the doctorate in different countries is given in

http://en.wikipedia.org/wiki/Doctorate

Dear Peter,

Thank you very much for the link. I just read it and it is informative.

Reginald

To attain a higher position of excellence in every (Philosophy and non-Philosophy)  field of study / research, attachment (LOVE)  to it  is more required. PhD requires a unbiased narrowed search into the chosen topic. Therefore the "love of wisdom" is polished and blemished over those years of intrinsic search period and evolve to become a staunch contributor to that field.. All areas of research are associated with loved wisdom. 

How Without any degree in Philosophy, one can become Doctor in that subject. Therefore Ph.D degree termology required to be discussed.

In academic discipline, Ph.D entails that the awardee is full of wisdom and knowledge, which connotes the original meaning of philosophy. Therefore, a Ph.D degree in any field connotes a degree in philosophy.

@Reginald please check this https://www.theclassroom.com/history-phd-degree-5257288.html