This week I’ve been talking about how the Supreme Court’s respect for its past decisions helps constitutional law to endure even as justices come and go. That doesn’t mean the justices have to live with every mistake from the court’s past. But it does mean they need to uphold some decisions that seem misguided, and even harmful, under their individual approaches to the Constitution. A commitment to precedent isn’t much of a commitment if it matters only when the stakes are low. That’s a point I think is worth underscoring, and one I talk about quite a bit in my book, “Settled Versus Right.”

Putting these ideas into practice requires drawing distinctions among the factors that might influence whether a decision is overruled. There are some reasons for reconsidering a decision that don’t depend on underlying views about how the Constitution ought to be interpreted. To return to an example I used yesterday, if certain facts were important to the court’s prior decision but have changed over time, that’s a good reason for taking another look. Recognizing that the facts have changed doesn’t depend on disagreements about constitutional interpretation. Facts are facts.

Other reasons — such as a justice’s conclusion that a prior decision is misguided or harmful — are harder to separate from broader questions about how the Constitution is understood and applied. Those questions are controversial and hotly disputed; they reflect different opinions among the justices (and among other judges, scholars and constitutional lawyers) about the proper way to interpret the Constitution.

If we think there’s value in trying to bridge these disagreements instead of rehashing them, we need a vision of precedent that generally disregards factors such as whether a decision is soundly reasoned and whether it has had negative consequences. Those sorts of factors would be natural to consider if the justices generally agreed with each other about how to approach the Constitution. Their shared understanding of which considerations are relevant (and which aren’t) would provide a basis for separating out the most glaring mistakes in the court’s past. But in a world of disagreement, even good-faith and principled disagreement, we need to exclude those factors to prevent disputes over constitutional philosophy from overtaking the role of precedent.

Most of the time, that is. Sometimes a justice views a prior decision as not just unsound and problematic but also exceptionally damaging under her theory of constitutional law. The decisions that fit this description will vary based on the types of considerations that an individual justice believes are relevant to interpreting the Constitution. For some justices, morality and fairness will have a central role to play. For others, key issues might involve original understandings, popular sovereignty or individual liberty. Whatever factors a particular justice thinks are relevant, we can imagine some decisions that she will view as exceptional in the harms they create.

In those exceptional cases, it makes sense for a justice to support an overruling based on her individual views about the Constitution. The theory of precedent I’ve defended asks the individual justice to defer to the Supreme Court’s history and institutional identity in upholding some decisions she thinks are wrong. That’s asking a lot, and there’s a limit on what we can reasonably expect. To my mind, the line is between decisions that a justice views as poorly reasoned and sub-optimal, and those that she views as disastrous in light of her approach to constitutional interpretation. Upholding decisions in the first category strikes me as an appropriate request, for the reasons I’ve talked about all week. But asking for tolerance of the second, disastrous category of decisions is asking too much.

Of course, any exception creates the possibility of weakening the rule. Still, I think it’s possible for Supreme Court justices to adopt a general practice of deferring to past decisions even as they occasionally invoke an exception for the worst of the worst cases. The key is to keep in mind that disagreement with a decision or discomfort with its results usually isn’t enough to overrule. If it were, the justices’ treatment of prior decisions would depend too heavily on their views about how to interpret the Constitution.

Where does that leave us? First and foremost, it leaves us with a baseline commitment to prior decisions even when today’s Supreme Court disagrees with them. Overruling a decision usually requires an objective reason — like a change in the facts — that isn’t tied up with big-picture questions about how judges should approach the Constitution. That requirement gives way only in cases that a justice views as the worst of the worst. When a justice thinks a prior decision’s rationale and results have been not just problematic but also disastrous, she is warranted in voting to overrule for that reason alone. But this exception needs to be tightly limited. Expanding it would entangle the treatment of past decisions with disputes about how to understand the Constitution.

This approach is consistent with the Supreme Court’s repeated descriptions of deference to past decisions as important but not absolute. Sometimes the mistakes of the past need to be corrected. But there’s also value in allowing the law to remain settled, and in keeping the court’s constitutional decisions from ebbing and flowing with changes in its personnel. There’s no mathematical formula that tells the court whether to overrule — not one that I’ve found, at least. That’s perfectly fine. The goal isn’t to work out an algorithm for overruling. The goal is to identify which considerations should matter and which shouldn’t, while always keeping in mind the reasons for deferring to past decisions in the first place.

One last point: Just because the Supreme Court won’t correct a mistake doesn’t mean we’re stuck with it. The solution is right there in Article V of the Constitution: the amendment power, which belongs not to the court but to the people and their representatives.

In tomorrow’s post, I’ll wrap up with some final thoughts about how past decisions are defined and applied.