There are three paradigmatic types of Supreme Court justices—the jurisprude, the ideologue, and the partisan. While no actual Supreme Court justice perfectly represents the ideal, some present pretty close approximations. It is hard to understand or predict the results of Supreme Court cases without determining how a particular justice fits into these types.
The jurisprude is a justice committed to a particular method of judging rather than an particular set of results. On the current Court the examples par excellence are Justices Antonin Scalia and Clarence Thomas who are committed to originalism. From the past Justice Hugo Black was a textualist and Felix Frankfurter, his sparring partner, advocated an historical jurisprudence. These jurisprudential commitments frequently lead to unusual ideological results. Justice Scalia (and Justice Thomas as well) vote for criminal defendants based on their close readings of the language of the Constitution, like the Confrontation Clause. For originalist reasons, Justice Thomas is no friend of preemption claims with the result that in his opinions businesses often lose to state tort law and regulation. Despite being a New Deal populist as a Senator, Black as a Justice wanted to enforce the Contract Clause against debtors.
The ideologue is a justice who is strongly right or left of center as that is defined in his day and votes that way.