Prevention or floor

A destination centered on keeping a critical variable above a minimum or stopping an unacceptable state from ever occurring.

Halfway up the trail, weather turning, one member of your group visibly gassed, someone says "we're so close to the summit." Every mountain accident report contains that sentence. In moments like this, average outcomes are irrelevant; what matters is that one unacceptable outcome never occurs, and summit enthusiasm is structurally biased against noticing.

Prevention or floor is the destination form built for asymmetric downside: the goal is keeping a critical variable above a minimum, or stopping an unacceptable state from ever happening, rather than maximizing anything. Use it when the downside is severe or irreversible and minimum adequacy beats average upside. The spec's required elements: the forbidden state or floor (no hike continues past the agreed turnaround conditions); who and when it covers (every member, every trip); an early-warning signal (daylight margin, the slowest member's condition); a response and escalation rule (turnaround is automatic, not a debate); and an explicit acceptance of residual risk, because zero risk is a fantasy. What changes: the group's worst decision gets made in advance, by calm people. The failure modes to avoid: demanding zero risk, letting the floor become the only objective, or tracking averages while rare catastrophic failures stay invisible.