also known as jacobus, he was born in the early 12th century and was an italian lawyer, one of four students of irnerius called the "quattuor doctores", although savigny disputes the general tradition of his inclusion in this list. the other doctors were bulgarus, martinus and hugo. the legal philosophy of bulgarus adhered closely to the letter of the law while their fellow, martinus took a more natural law and equity approach. his time at bologna was therefore one of the formative times in legal theory.