Well, the STB is a Bachelor’s degree, the STL is the licentiate (equivalent to Master’s in some European systems), and the STD is the doctorate.
It’s difficult to make a comparison to secular degrees, but I’d presume that the STL is roughly equivalent to the M.Div. at a Protestant divinity school, and the STD to a D.D. There is no Protestant or secular Bachelor in Theology that I’m aware of, so I don’t think it has an equivalent. However, I believe most Catholic seminaries award it concurrently with the secular M.Div.
