Reason upward

Skill chrisdavidson/first-principles-skill/first-principles/skills/reason-upward

Claude Code plugin for systematic first-principles thinking — a 5-phase methodology (identify essence, challenge assumptions, establish ground truths, reason upward, validate) plus 13 companion skills. Installable via the Claude Code plugin marketplace; every conclusion traces back to a verified ground truth, not to analogy or convention.

Install

npx -y skills add chrisdavidson/first-principles-skill --skill reason-upward

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Slash-only Phase 4 stub — build derivation chains upward from named ground truths.

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SKILL.md

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Focused Reason Upward Mode

You are running in focused-reason-upward mode. Execute only the procedure below and produce only its canonical output sections — do not run the full 5-phase first-principles analysis. Skip Step 0 technique selection; the user has already chosen this technique by invoking the slash command directly.

When to reach for this

Use this phase once the Ground Truths list is complete — all ground truths carry IDs and verification notes — and the Classified Assumptions Table from Phase 2 is finalized. The methodology has established what is true (ground truths) and what can be discarded (false assumptions). The task now is to construct an answer from those truths. This phase is deliberately high-freedom because the right method for combining ground truths depends entirely on the problem's structure.

Procedure

Reason upward from the ground truths toward an answer using whatever approach the problem calls for. As you go, narrate what you are trying, what you are building on, and why — reasoning is free-form, but it must be self-documenting. If a reasoning path leads to a dead end, record it in the Abandoned Reasoning section before changing course; do not quietly discard a path that might matter to someone reviewing the analysis. Do not use analogies as direct evidence — any reference to how others have solved similar problems must be grounded in a verified ground truth about their situation, not used as standalone justification. Before handing off to Phase 5, apply the second-order effects procedure to extend the relevant Derivation Chain with 2nd/3rd-order effects. If any extension step contradicts a Ground Truth, the conclusion returns to Phase 2 for re-challenging.

Named artifact: Derivation Chains — one chain per conclusion, formatted as GT-N + GT-M → [intermediate claim] → [conclusion], with confidence levels per D-07. Each chain must include at least one intermediate step; a chain that goes directly from ground truth IDs to a conclusion is a flat list, not a derivation.

Exit criterion: ALL THREE conditions must hold: (1) the problem's core question as stated in the Essence Statement is answered, AND (2) every conclusion offered has a complete derivation chain back to named ground truths, AND (3) the second-order effects procedure pass has been applied and no extension step contradicts a Ground Truth. Partial conclusions, incomplete chains, or a silently-skipped second-order pass do not satisfy this criterion and do not exit this phase.

If a fuller analysis is needed afterward, invoke the main first-principles agent with this output as Known ground truths.