This much is clear after two hours of Supreme Court arguments over the constitutionality of the individual mandate, which I was in the room to hear: The president's health-care bill won't rise or fall on a question of law, but on how the majority of justices define the health-care market.

 The mandate requires all individuals above a certain income level to obtain health-care coverage. The National Federation of Independent Business and 26 states challenged the mandate as unconstitutional, arguing that Congress does not have the power to force individuals to buy private products. The government, for example, has the power to regulate the kind of muffler your car has, but it cannot force you to buy a car in the first place. Health-care should be no different — a point made forcefully at various times by Justices Antonin Scalia and Samuel A. Alito. If the government can mandate the purchase of health care, Scalia said, “what else can’t it do?”

Justice Stephen Breyer appeared to see the mandate and the market from a completely different point of view. Breyer at one point suggested that everyone automatically becomes a participant in the heatlh-care market as soon as they're born. Because no human being can escape illness, Breyer said, everyone will at some point require medical services; this includes those who cannot pay or those who lack insurance. Justice Ruth Bader Ginsburg, who embraced the same vision of the health-care market, argued that a person's refusal to buy health insurance is actually a choice to pass on potential health-care costs, and “they're making the rest of us pay for it.” Justices Sonia Sotomayor and Elena Kagan appeared on board with their fellow Democratic appointees.

Both Chief Justice John Roberts and Justice Anthony Kennedy were obviously troubled by the prospect of an all-powerful federal government. “All bets are off,” Roberts said, if the court signs off on Congress's constitutional power to force individual purchases of health insurance.

Both also seemed at points receptive — albeit grudgingly — to arguments that the market for health care is unique and requires special consideration. Kennedy in particular seemed to soften near the end of the hearing, acknowledging the problem of the millions who are uninsured and pondering out loud about how the government could address that.

 Predicting how justices will vote is always risky business. But I'd say there is still a good chance that the mandate is upheld by a 5-4 or 6-3 vote, with Kennedy in the majority in the first scenario and Kennedy and Roberts part of the six-justice majority in the latter.