Is PhD the highest degree one can earn?

There are several higher doctorates awarded by universities, including Doctor of Philosophy (Ph.D.), Doctor of Letters (D.Litt.), and Doctor of Science (D.Sc.).

PhD is probably the most well-know higher doctorate in the world, but not the highest degree one can earn. The PhD applies to graduates in a wide array of disciplines in the sciences and humanities, and it has become a requirement for a career as a university professor/lecturer or researcher in many fields.

In the UK, the degree D.Litt. is a higher doctorate, above the PhD, and is issued on the basis of a long record of research and publication. The D.Litt. is awarded to candidates whose record of published work and research shows conspicuous ability and originality and constitutes a distinguished and sustained achievement. University committee and board approval is required, and candidates must provide documented mastery of a particular area or field. In the US, the degree is almost always an honorary degree often conferred to those who have contributed to the humanities or society.

I first heard of the degree Doctor of Letters in my PhD graduation ceremony. It was awarded by my university to a famous playwright as an honorary degree.

In the UK, the degree of Doctor of Science is probably the Highest Doctorates, typically is conferred on a member of the university who has a proven record of internationally recognised scholarship. A candidate for the degree will usually be required to submit a selection of their publications to the board of the appropriate faculty, which will decide if the candidate merits this accolade. The degree will only exceptionally be awarded to a scholar under the age of forty. The status of the degree has declined because it is not widely understood, but in former times the doctorate in science was regarded as a greater distinction than a professorial chair. The Doctor of Science may also be awarded as an honorary degree, that is, given to individuals who have made extensive contributions to a particular field and not for specific academic accomplishments.

I heard of the D.Sc. when a colleague of mine who is a professor was award the degree by our university. I asked him, "You have already a PhD degree long time ago. What's the difference between this doctor degree and the PhD?" I was told then that the Doctor of Science is even greater than the professorship and is the highest doctorate one can get in UK, though it might have different meaning in other countries.