Many American presidents have been lawyers, but almost none have come to office with Barack Obama’s knowledge of the Supreme Court. Before he was 30, he was editing articles by eminent legal scholars on the court’s decisions. Later, as a law professor, he led students through landmark cases from Plessy v. Ferguson to Bush v. Gore. (He sometimes shared his own copies, marked with emphatic underlines and notes in bold, all-caps script.)

Now Mr. Obama is preparing to select his first Supreme Court nominee to replace retiring Justice David H. Souter. In interviews, former colleagues and students say they have a fairly strong sense of the kind of justice he will favor: not a larger-than-life liberal to counter the conservative pyrotechnics of Justice Antonin Scalia, but a careful pragmatist with a limited view of the role of courts.

“His nominee will not create the proverbial shock and awe,” said Charles J. Ogletree, a Harvard professor who has known the president since his days as a student.

Mr. Obama believes the court must never get too far ahead of or behind public sentiment, they say. He may have a mandate for change, and Senate confirmation odds in his favor. But he has almost always disappointed those who expected someone in his position — he was Harvard’s first black law review president and one of the few minority members of the University of Chicago’s law faculty — to side consistently with liberals.

Former students and colleagues describe Mr. Obama as a minimalist (skeptical of court-led efforts at social change) and a structuralist (interested in how the law metes out power in society). And more than anything else, he is a pragmatist who urged those around him to be more keenly attuned to the real-life impact of decisions. This may be his distinguishing quality as a legal thinker: an unwillingness to deal in abstraction, a constant desire to know how court decisions affect people’s lives.

“The University of Chicago was and is full of eminent theorizers who wrap up huge areas of the law by applying some magic key,” said David Franklin, a former student. “He didn’t do any of that; he wasn’t interested in high theory at all.”

Though Mr. Obama rarely spoke of his own views, students say they sensed his disdain for formalism, the idea — often espoused by Justices Scalia and Clarence Thomas, but sometimes by liberals as well — that law can be decided independent of the political and social context in which it is applied. To make his point, Mr. Obama, then a state senator, took students with him to Springfield, Ill., the capital, to watch hearings and see him hash out legislation.