necessity-sufficiency

Necessity-Sufficiency Strategy

PNS/PS framework: classify each factor by its causal role — necessary, sufficient, both, or neither.

Method

1. causal-claim-extraction identifies all causal claims
2. factor-enumeration lists candidate causes
3. necessity-evaluation tests: would conclusion fail WITHOUT this factor? (PN)
4. sufficiency-evaluation tests: would this factor ALONE produce conclusion? (PS)
5. single-factor-removal provides evidence for necessity judgments
6. load-bearing-identification classifies factors into quadrants

Classification Quadrants

• Necessary + Sufficient: Load-bearing walls (removal collapses conclusion)
• Necessary + Not Sufficient: Required but not enough alone
• Not Necessary + Sufficient: Redundant paths to conclusion
• Neither: Decorative factors (safe to vary)

Budget Table

Parameter	S	M	L
Factors tested	5	10	20
Necessity evaluations	3	6	12
Sufficiency evaluations	3	6	12

Orchestration

causal-claim-extraction → factor-enumeration
→ [for each factor]:
    necessity-evaluation (PN score)
    + sufficiency-evaluation (PS score)
    + single-factor-removal (supporting evidence)
→ load-bearing-identification (quadrant classification)

Subagents

• causal-claim-extraction (claim identification)
• factor-enumeration (candidate listing)
• necessity-evaluation (PN scoring)
• sufficiency-evaluation (PS scoring)
• single-factor-removal (evidence generation)
• load-bearing-identification (classification)

Available Tactics

Optional, no fixed order; the final leaf is always a sop.

Tactic	When to use
causal-necessity-testing	Tactic: Extract causal claims, evaluate probability of necessity (PN) and sufficiency (PS) for each, classify into necessity-sufficiency quadrants.
systematic-factor-ablation	Tactic: List all factors, remove one at a time, assess conclusion stability, rank factors by load-bearing importance.