Nobody knows what the Supreme Court will decide with regard to the Affordable Care Act. But, after this week’s hearings, it seems quite possible that the court will strike down the “mandate” — the requirement that individuals purchase health insurance — and maybe the whole law. Removing the mandate would make the law much less workable, while striking down the whole thing would mean denying health coverage to 30 million or more Americans.

Given the stakes, one might have expected all the court’s members to be very careful in speaking about both health care realities and legal precedents. In reality, however, the second day of hearings suggested that the justices most hostile to the law don’t understand, or choose not to understand, how insurance works. And the third day was, in a way, even worse, as antireform justices appeared to embrace any argument, no matter how flimsy, that they could use to kill reform.

Let’s start with the already famous exchange in which Justice Antonin Scalia compared the purchase of health insurance to the purchase of broccoli, with the implication that if the government can compel you to do the former, it can also compel you to do the latter. That comparison horrified health care experts all across America because health insurance is nothing like broccoli.

Why? When people choose not to buy broccoli, they don’t make broccoli unavailable to those who want it. But when people don’t buy health insurance until they get sick — which is what happens in the absence of a mandate — the resulting worsening of the risk pool makes insurance more expensive, and often unaffordable, for those who remain. As a result, unregulated health insurance basically doesn’t work, and never has.