As stated by James Hall and Langdell, two people who were involved in the creation of the J.D., the J.D. is a professional degree like the M.D., intended to prepare practitioners through a of analysing and teaching the law through logic and adversarial analysis (such as the casebook and Socratic methods). It has existed as described in the United States for over 100 years, and can therefore be termed the standard or traditional J.D. program. The J.D. program generally requires a bachelor's degree for entry, though this requirement is sometimes waived. The program of study for the degree has remained substantially unchanged since its creation, and is an intensive study of the substantive law and its professional applications (and therefore requires no thesis, although a lengthy writing project is sometimes required). As a professional training, it provides sufficient training for entry into practice (no apprenticeship is necessary to sit for the bar exam). It requires at least three academic years of full-time study. While the J.D. is a doctoral degree in the US, lawyers usually use the suffix "Esq." as opposed to the prefix "Dr."