|A more realistic model of justice
People have an idealistic mental model of how a Supreme Court justice might arrive at judgments by carefully pouring through the question and the legal principles to arrive at a conclusion. Most people have that model, but almost nobody actually believes it. Others assume that ideology is the entire explanation and that the opinions of the court are just voluminous ideological screeds. They explain away unexpected decisions as shifts in a judge's ideology or revelations about a judge's true ideology.
A more realistic model for how justices decide is a mixture. More likely what happens is that a judge begins from the conclusion they would like to reach and then they attempt to construct a solid justification for it. They may do the same for alternate conclusions, but they almost certainly spend less effort looking to justify the conclusions they don't want to reach. Perhaps they assign a clerk to construct an alternate conclusion so they can then ignore it.
Recent leaks combined with the contents of a very mixed opinion constructed by Justice Roberts reveals the reality in more detail. Too many people with opinions seem not to know that Roberts actually did strike down the individual mandate, making clear that direct criminal penalties to force commercial activity is an overreach of federal power -- he just upheld the enforcement provision as a legitimate free-rider tax. We now know that Roberts sided with a 5-4 conservative majority to strike the mandate, but as he was constructing the majority opinion, he made a subtle change that flipped that picture. By the time he was done writing it, he had finished writing the 5-4 liberal majority decision. How did that happen?
It shouldn't be too big of a shock if you read the law closely. Suppose you imagine writing the decision to strike down the individual mandate -- if you don't have a basic understanding of law, stop here for a refresher on the commerce clause, the necessary and proper clause, the taxing and spending clause, and the sixteenth amendment....
Back to the story, suppose you've already decided to strike down the individual mandate as "not a valid exercise of Congress’s power under the Commerce Clause and the Necessary and Proper Clause" and you've even essentially finished constructing that part of the decision but you are now deciding how to "sever" the individual mandate from the rest of the bill in writing the conservative majority decision to declare it unconstitutional. At least one extreme right wing judge who saw the case before it reached the Supreme court decided that the mandate is inextricably linked to the entire law and thus the entire law must be voided, and people who understand the policy understand that it is linked to the provision that prevents insurance companies from denying coverage based on pre-existing conditions, but the role of the court is generally to rule narrowly and leave policy decisions to the other branches of government. The court severs narrow provisions of a law based on what is possible and constitutional, not based on what is good policy.
So where can you sever it? Even for one who has already decided to strike the mandate, it's not entirely obvious. You have to ask a few questions. Where does the constitutional part end and the unconstitutional part begin? At some point, the exercise probably involves reading the law.
One colorful approach might be to start by striking as narrowly as possible just a few words and phrases that make it clear that it's unconstitutional. In this case, the words "requirement" and possibly "penalty" seem to be the ones [the word "mandate" is not actually found anywhere in the "Individual Responsibility" section of the law]. From there, strike any sentences or paragraphs that have become too nonsensical to implement. Finally, any parts of the law that become physically or logically impossible to implement without the stricken parts are also stricken. What is left?
Another approach is to imagine the law written in an alien language and you are an observer incapable of learning the language but able to watch every aspect of it being enacted and enforced. From there, strike any operations, behaviors, or enforcement actions that violate your concept of constitutional federal powers and then write whatever law is left in your own language to reflect what you see as its true meaning. What is left?
There are plenty of other ways, and I doubt these colorful approaches actually reflect Roberts' thinking, but it is interesting to note that they both lead to exactly the same conclusion! The first approach leads one to "strike the mandate" but leave its enforcement in place as a tax incentive. The second leads one to declare that it always was nothing more than a tax incentive, but because of the misleading "requirement" language, the court voluntary offers the opinion for future laws that such a mandate would be unconstitutional.
In other words, Roberts started from the conclusion to strike the mandate and his position never changed! The only thing that changed was his discovery that the free rider tax can be construed as a tax, severed from the mandate, and that the only justification for striking the tax under that interpretation would be purely ideological and not legal! And what ideology? The individual mandate was first proposed by conservatives as a "tax on free riders to promote individual responsibility," it was not popular with liberals, Newt Gingrich promoted it, and Romney implemented it. Many liberals still see it as a giveaway to the insurance industry, and usually it's the conservatives who bend the rules to protect corporate power and profit. Lucky for Roberts, he was not asked to resolve that question.
So he didn't change his mind, but merely made a discovery. When he made that discovery, he certainly brought it to the attention of the other conservatives. How many of them do you think cared about the legal reasoning? Roberts was not arguing, he was tasking them with the job of rationalizing their pre-determined dissent as he was giving up that task. In Gonzales v Raich, even Scalia decided that the Commerce Clause and the Necessary and Proper Clause could be used by the federal government to criminalize non-commercial behavior legal within a state if indirectly necessary for other measures to have force! He cited precedent, though he has since wavered in his support for that precedent, but given that his decision in Gonzales actively denied medical treatment, perhaps the true deciding factor is that he opposes expanded access to healthcare. Maybe not, but he makes it way too easy.]
One might be surprised that Roberts was the only one who changed his mind until you realize that he was the one constructing the majority opinion [the only important opinion], and it seems it was the act of constructing that opinion that forced him to recognize the more nuanced reality. So we have an answer, for Roberts at least. Like any other human, he is flawed. He most certainly started from his conclusion and constructed the opinion from there, but a majority opinion is not just an ideological screed. Scalia might wish to live in an oligarchy where all resource allocation is decided by a ruling class of wealth elites, and he might think it is moral and just and right, but at some point along the way, even he would have to construct serious legal arguments to support that position as a Justice of the Supreme Court.