Legal reasoning by precedent operates on an elegant assumption: similar cases should be decided similarly. When a court faces a novel dispute, lawyers present prior decisions as evidence of how the matter should resolve. The doctrine of stare decisis gives this process its legitimacy, creating predictability and stability in the law. Clients can plan their affairs knowing that courts will treat them as they’ve treated others before.
This approach works remarkably well for its intended purpose. If you want to predict how Judge Smith will rule on a motion to dismiss in a breach of contract case, studying her prior rulings on similar motions is genuinely useful. Judges themselves rely on precedent. They’re trained in the same tradition, and professional norms encourage consistency. When everyone in the system is playing by the same rules, backward-looking reasoning becomes self-fulfilling prophecy.
This is exactly why precedent-based reasoning remains the right tool for legal analysis. When advising a client on contract enforceability, litigation risk, or regulatory compliance, we should absolutely study how courts and agencies have handled similar matters. The institutional commitment to consistency makes the past a reliable predictor of the future.
The Map No Longer Matches the Territory
Consider the lawyer deciding whether their firm should invest heavily in AI-powered research tools. Will these tools deliver enough efficiency gains to justify the cost? How quickly will competitors adopt similar technology? Will clients soon expect, or even demand, that their counsel use these capabilities?
These are not legal questions. They are business and strategic questions. And yet lawyers must answer them constantly, both for their own practices and in guiding their firms’ futures. Try answering them using precedent. You might examine how firms responded to previous technology waves: Westlaw in the 1980s, email in the 1990s, cloud computing in the 2000s.
But this analysis immediately runs into problems. Each of those transitions occurred at a different pace, with different competitive dynamics, and with tools of fundamentally different capability. The “precedent” of prior technology adoption may be not just unhelpful but actively misleading, anchoring your strategic thinking to conditions that no longer exist. The firm that waited five years to adopt email suffered few consequences; the firm that waits five years to integrate AI may find itself unable to compete on cost or speed.
Daniel Kahneman, in his research on judgment and decision-making, identified what he called the “planning fallacy,” our systematic tendency to underweight new information while overweighting our existing mental models. Lawyers may be particularly susceptible to this bias. Our entire training reinforces the authority of the past. When faced with novel strategic questions about our own practices and careers, we instinctively reach for analogies and historical patterns, even when those patterns have limited predictive value.
We think: “Lawyers survived the introduction of the Cloud, so we’ll survive AI.” But this reasoning by analogy obscures more than it illuminates.
The Bayesian Alternative
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