Reading the question posted here left me with a more general question:
Given the professional title and name: Dr. (First Name)(Last Name), is there some way to differentiate between the holder of a philosophical doctorate and a medical doctor? Wouldn't it be more appropriate for a PhD holder to have the title (First Name)(Last Name), PhD?
You can't immediately tell from the title, but then titles are not typically used by an individual to broadcast their occupation - we don't have variants of "Mr" for plumbers, bank managers, or rock stars - despite their very different occupations. Rather, the title is to be used by others when addressing that individual, in order to signify a degree of respect, typically for a particular level of training, qualification and responsibility, or else for a particularly respected position in society. Even the term "mister" is a meaningful sign of respect that historically would not have been as widely applied as it is today - the ratchet of etiquette has gradually eliminated everything below it.
The actual title "Doctor" means "teacher" (from Latin "doceo", "I teach"). This title is more often more relevant to PhDs than MDs, so you probably have your suggested solution backwards. That said, the solution is really neither necessary nor appropriate. Much like "Master" (from Latin "magister", in this case "teacher"), "Doctor" signifies that an individual has not only gained enough competency to practice in a particular field, but has developed enough expertise to instruct others. An individual who is sufficiently qualified to practice but not teach would historically have been known as a "journeyman", roughly equivalent to "professional".
In short "doctor" refers not to a field of expertise, but rather to a level of expertise.
Incidentally, most UK surgeons drop their title of "Dr" and revert to "Mr" after joining the Royal College of Surgeons. I've heard through a friend of at least one surgeon who reacted quite angrily at being addressed as a mere "Dr", which in such circles, due to a collision between traditional titles and modern medical training, could be unkindly translated as "trainee".
You can't. That's why there are numerous jokes in English-speaking culture about whether someone addressed as "doctor" is a "real" doctor or not. Medical doctors are supposed to be the "real" ones in the jokes.
In the United States, in spoken address, both are called "doctor."
For personal correspondence, both are addressed as "Dr." as with an invitation addressed to "Dr. and Mrs. Smith." (Or maybe "Dr. and Mr. Smith." If they both hold doctorates, it is "Drs. Smith." For a couple with different family names, use "Dr. Smith and Mr. Brown.")
For professional correspondence, both are addressed by name and degree, as "James Smith, M.D." or "Bob Brown, Ph.D."
Since the distinction is only relevant in professional interactions, there really isn't any ambiguity.
If you are speaking to a medical doctor professionally, you will know it by the setting, and you still say "doctor." If you ask for medical advice at a cocktail party because someone was introduced as "doctor" you deserve anything you get! I've been known to say, "I'm a college teacher type doctor, not a take-off-your-clothes doctor." That usually sends the message and often gets a laugh.
I have seen the difference in the written form of their name;
One is Name Family, PhD. and other one is Name Family MD.
The same applies to the people holding Engineering doctorates such as Name Family, EngD. or holding doctorate in business such as DBA. Also, in different countries there are usually different doctorate titles (link) awarded.
But all of these people are called doctors.
A medical practitioner usually holds a MBBS or MD degree or similar and - at a reasonable level of proficiency - membership of a professional body such as the AMA ( American Medical Association) or the RCP ( Royal College of Physicians) or whatever applies in their part of the world.
A holder of an academic doctorate ( PhD, DrPh, EngD etc) has researched a topic or problem within their specific subject in sufficient depth to have generated fresh insights or made a breakthrough or contributed significant new knowledge to the existing corpus.
Both have earned the right to be addressed as 'Dr'.
However, it would appear to me that one or two posters have been watching a few too many episodes of 'The Big Bang Theory' as I think the need to differentiate between the two very rarely applies except in a medical emergency.
While both have the title of "doctor," that is identifying the fact that they both have the same education level, a doctorate.
The meaningful difference here is occupation: one might be a professor, the other a physician.
To differentiate between the two you can use the actual doctorate type or the job title:
Of course a physician could also be a professor (who teaches in medical school?), or an M.D. might be a researcher who does not treat patients as their primary means of income (i.e. they only deal with patients during the course of medical studies). I do not think you can do much about those cases.
In Germany, it is common to denote the subject area the doctor was obtained in, such as Dr. med. for medical doctors, Dr.-Ing. for engineers, or Dr.-rer-nat. (rerum naturalium) for sciences like chemistry.
The usual practical solution is "ask them."
Doctor means you have a doctorate. Simple as that, a medic can have a doctorate in medicine and thus be a doctor, but if you do not have the degree then you are not a doctor, you can be a surgeon or a licensee of medicine but you are just referred to as doctor out of colloquial use of the title based on historical rots and customs.
There is no difference in spoken address ('Doctor'), but one is a Ph.D. and the other is an M.D.
You can tell from the context, but without the context, you can't. If the context is obviously far removed from anything clinical, such as "Dr. xyz has written a book on archaeology of early Los Angeles", then it's obviously the PhD sense. If it's a clinical setting, including emergencies and simply asking for health advice, basically when someone's health is at stake, then it's obviously the MD sense.
Things can get more ambiguous in biomedical research, because I personally know some MDs (without PhD) doing research instead of practicing medicine, including some molecular biology professors. When a research paper that uses clinical samples says something like, "Samples were obtained after resection from Dr. xyz", then it really can be either MD or PhD or both. Some people in our field have both.
Anyway, I don't make too big a deal out of it because we in California are typically on first name basis outside the clinical setting (this includes medical doctors). When we PhDs and candidates (at least in CA) say "doctor", we also usually mean medical doctors, like in, "Our postdoc health insurance is so bad that I'm terrified of seeing a doctor", where "doctor" obviously doesn't refer to ourselves. Some states, including California, have laws forbidding anyone who is not a medical doctor to advertise themselves as Dr. something in order not to confuse patients.
The confusing aspect is that doctor connotes medical treatment to most people, not a doctoral degree. Anyone smart enough to have a PhD knows the difference. I would not want a PhD doing my surgery, nor an MD teaching me philosophy.
It's not an easy question to answer. Ph.D's who are professors are just called "professor," and research assistants with a Ph.D are called "doctor" by secretaries and students. Titles are never mentioned in academic papers.
It's different with doctors: Patients and nurses call them "doctor;" if they are also professors, which they often are, the are called "professor" since professors have a higher status than mere M.D.s, and when they write papers in medical journals they put M.D. after their names. When practitioners without an M.D. refer to themselves as "doctor" they are just called "frauds."
Things are much more interesting in Germany. I was treated there by a woman doctor in a University Hospital who was also a professor of medicine. Her title was Frau Dr. Med, Dr. Professor Mueller. Some Professors have three degrees, meaning that are called Herr (or Frau) Dr. Dr. Dr. Professor.
In French (maybe other latin countries too), but I don't know about English, you can make a small difference by adding ès : Albert Einstein, Docteur ès Physique.
Then twice in a row you have specified that he was a scientific doctor (not a medical one) and his field of research.
