There are only two types of Doctor's degrees. Earned and Honorary.
An earned doctorate is an educational degree. It is bestowed on a graduate by his college or university upon his fulfillment of that school's requirements for such a degree. This involves certain academic achievements and acknowledges the graduate's mastery of a broad field of knowledge. Some common earned degrees are:
M.D. Doctor of Medicine
Ph.D. Doctor of Philosophy
Th.D. Doctor of Theology
Ed.D. Doctor of Education
An honorary doctorate is just that. It is bestowed upon the recipient by some college or university as a way of honoring him or her for some outstanding merit, or service to that school. It must be remembered though that an honorary degree cannot bestow an "instant" expertise in the area named, any more than bestowing a degree on Dorothy's Scare Crow" gave him a brain. The recipient of an honorary degree would know no more about Bible manuscripts after he received his degree than before he did. It is an honor only, not an academic degree. (No one would wish to be operated on by a surgeon with an "honorary" degree.) Their opinion on Bible questions certainly wouldn't outweigh the findings of an earned degree. Or even of someone who holds no degree but has thoroughly investigated all of the available evidence. Academically, an honorary doctorate is like an "honorary black belt" in karate. Wear it around the house, but don't try to use it or you'll get killed!
Some common honorary degrees are:
D.D. Doctor of Divinity
D.Mus. Doctor of Music
D.Sc. Doctor of Science
L.H.D. Doctor of Human Letters
Lit.D. Doctor of Literature (or D.Lit.)
L.L.D. Doctor of Laws
Litt.D. Doctor of Letters
Both types of degrees have their place. The honorary degree is very much a badge of merit, and should be respected as just that. An honor bestowed upon the individual for his meritorious deeds performed for Christ or his school.
The earned degree is an academic title and stands on the merit of the education that it represents.