WASHINGTON (AP) _ There is something liberating about a lifetime appointment and a certainty in the correctness of one's ideas. Justice Antonin Scalia has both.

He travels the world as a sought-after speaker, snags White House dinner invitations and packs one of the most powerful pens on Earth as a leading conservative voice on the U.S. Supreme Court. More than once, he has looked over a crowd of Washington power-brokers and observed that there is no one in the group who can help him or hurt him.

Yet while Scalia's influence and presence are undisputed, there have been significant frustrations as well as victories for him during his two decades on the court. The year's new term begins Monday.

Early optimism that his affability would allow him to serve as a consensus-builder is long gone, buried under a heap of biting opinions and acerbic observations about the reasoning of fellow justices and others.

Now, with a judicial deck that has been reshuffled over the past year by the arrivals of John Roberts and Samuel Alito, Scalia has fresh hope of reinforcements for some of his most strongly held views. But he also faces potential new sources of discouragement.

``It has to be frustrating to Scalia that now, 20 years in, he's still sitting on a court that does not have a predictable, constant, consistent five-person majority for the things that he cares about, and that's sort of a remarkable thing,'' said Stephen Wermeil, a law professor at American University.

Still, says Wermeil, ``There is always a new-kid-in-the-sandbox kind of phenomenon. It's exciting and it changes the dynamic by which everybody else interacts.''

Scalia, whose 20th anniversary on the court came and went quietly this week, was passed over by President Bush in favor of Roberts for the position of chief justice when William Rehnquist died a year ago. Scalia told reporters at the time, ``I'm not even sure I wanted it, to tell you the truth,'' saying the chief justice's administrative duties would have taken time from his thinking and writing.

And Scalia, who relishes verbal jousting, has to be pleased with how things are working out. Roberts is believed to be allowing more give-and-take among the justices than did Rehnquist, who controlled conference sessions with a tight rein.

Roberts and Alito stand solidly with Scalia and Clarence Thomas in the nine-member court's conservative bloc, but the new term will tell more about the distinctions among their judicial philosophies.

For example, Roberts tries to resolve cases on very narrow grounds, which is ``somewhat in tension with the desire of Justice Scalia to engage the merits'' of cases that come before the court, said Pepperdine law professor Douglas Kmiec.

David Garrow, a Supreme Court historian at Cambridge University, agreed that while the court is likely to shift to the right overall, ``Scalia may find himself with a new conservative chief justice who agrees with him in the abstract but as a matter of judicial discretion and judicial philosophy believes the court should always pull its punches rather than go to the mat.''

Scalia, along with other justices, will have to pay particular attention to Anthony Kennedy, who has emerged as the court's crucial swing vote since the retirement of Sandra Day O'Connor. Kennedy is known as a thinker who likes to think out loud, even wrestling with pros and cons in his written opinions, a style that couldn't be more different from Scalia's certitude.

``It's always frustrating for someone who sees things quickly and easily and in a clear fashion to come up against someone more deliberative,'' Kmiec said of the Scalia-Kennedy interplay. ``You can see the objective clearly and you wonder why others don't.''

Scalia, of course, has been there, done that before with O'Connor.

His impatience with the reasoning of fellow justices sometimes comes through clearly in his writings, as in his 1989 dissent from an O'Connor opinion that he said was ``irrational'' and ``cannot be taken seriously.''

At the same time, however, he can be charming, even with those with whom he disagrees. His closest friend on the court remains Justice Ruth Bader Ginsburg, ideologically poles apart from Scalia.

At age 70, Scalia shows no interest in retiring, or signs of mellowing.

An analysis by Boston University associate law professor Jay Wexler of which justices provoked the most laughter during oral arguments in the 2004-2005 term gave top honors to Scalia in a landslide.

His sharp wit comes with a thin skin.

In March, he wrote a biting letter to the editor of The Boston Herald after the newspaper reported he had made an obscene gesture at a reporter who questioned him about his attendance at a special Red Mass for lawyers. In the letter, Scalia explained at length that the gesture, flicking his fingers under his chin, was a jocular way to communicate that ``I couldn't care less.''

He said he made the gesture at the reporter, whom he described as ``an up-and-coming 'gotcha' star,'' after she asked whether his attendance at the Mass might raise questions about his impartiality in matters of church and state.

``From watching too many episodes of the Sopranos, your staff seems to have acquired the belief that any Sicilian gesture is obscene _ especially when made by an 'Italian jurist,''' Scalia wrote. ``(I am, by the way, an American jurist.)''

Hand gestures aside, Scalia does care, though, and care deeply about the law of the land.

And that means that the reconstituted court holds great potential for him but also the possibility for further disappointment, just as the two court appointments of Bill Clinton in the 1990s kept his views from prevailing in earlier terms.

``For Scalia, the next decade promises excitement, promises the potential for victorious coalitions and I think he's looking forward to it,'' said University of Connecticut political scientist David Yalof, who specializes in constitutional law. ``The caveat is that he probably went into the 1990s with similar hopefulness and excitement.''

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