triangulate-sources

name	triangulate-sources
description	Establishes one claim by independent corroboration — gathering candidate sources, grading each, collapsing those that share an author, a first-hand root document, a publication event or an incentive structure, and reporting whether at least two genuinely independent sources agree. Use when one source is not enough to rely on a claim — "corroborate this claim", "find independent confirmation", "do these sources really agree or are they all quoting the same press release?", "triangulate this figure". Not for grading a single source (use `rate-source-admiralty`) or vetting an unfamiliar site laterally (use `sift-source-check`).
license	MIT
metadata	{"category":"evidence-verification","method":"Source triangulation (data triangulation applied to sourcing)","origin":"Norman K. Denzin, 1978; ICD 206 sourcing standards, 2015","version":"2.0.0"}

Triangulate Sources

Triangulation is Norman Denzin's discipline (The Research Act, 2nd ed., 1978) of establishing a finding by approaching it from several directions — his typology distinguishes data, investigator, theory and methodological triangulation. This skill applies the data-triangulation branch to sourcing: a claim counts as established only when two or more genuinely independent sources assert it. The core principle is that independence, not count, is what carries the weight — the same discipline the intelligence community codifies in ICD 206 (2015), which strongly encourages a source summary statement covering "what sources are meaningfully corroborative or conflicting" and says a citation "should reference the most original source" rather than a re-report. The four independence tests in step 4 are this skill's own instrument: neither Denzin nor ICD 206 supplies a test list, a collapsing rule or a count threshold. The failure it prevents is manufactured consensus: five articles that all trace to one press release look like five confirmations and are one.

When to invoke

Invoke when:

• A claim is load-bearing enough that a single source is not sufficient: a headline conclusion, a recommendation, an executive-summary figure, a quantitative claim about a market, a funding amount, or a valuation.
• The question is explicitly about corroboration: "corroborate this claim", "find independent confirmation", "do these sources really agree?", "triangulate this figure".
• Several sources appear to agree and it matters whether they are echoing one another.

Do NOT invoke when:

• The task is grading how trustworthy one source is — use rate-source-admiralty; this skill calls that one per candidate.
• The source is unfamiliar and has not been vetted at all — run sift-source-check first.
• The claim is peripheral colour or already hedged; corroboration costs lookups, so reserve it for claims a reader would act on.
• No independent source can be found, or the sources conflict irreconcilably — hand the claim to abstain-or-escalate rather than forcing a verdict.

Procedure

1 — State the claim in one specific sentence

Write the claim with its subject, value, unit and date: "Company X closed a $3.5 billion Series E at a $61.5 billion post-money valuation in March 2025". A vague claim cannot be corroborated, because different sources will be agreeing about different things. Everything downstream is judged against this sentence.

2 — Gather candidate sources

Collect three to five candidates that assert the claim, from as many different kinds of origin as available: primary records (filings, registries, standards, court documents), the party's own announcements, independent reporting, and specialist or academic literature. Record each candidate's originator, date, and the first-hand evidence it points to.

3 — Grade each candidate

Grade every candidate with rate-source-admiralty — reliability letter, credibility digit, one-sentence rationale. The grade does not decide independence, but it decides which source survives when a cluster is collapsed in the next step, and it keeps an F-graded source from silently counting as corroboration.

4 — Apply the four independence tests

Two sources are independent only if all four hold. Any failure means they are one source in different clothes. One documented exception: where a source that shares a root nonetheless contributes a separable first-hand element of its own — a named interview, an independent record check, a measurement it made — it may be counted, provided the judgement and what the source added are written into rationale. An undocumented exception is a failed test.

Test	Independent when	Collapses when
Different originator	Different author, newsroom or organisation	One quotes or syndicates the other; both carry the same byline
Different first-hand root	Each traces to a different underlying document or observation	Both trace to the same filing, release or dataset
Different publication event	Each adds content or observation of its own	One is a repost, update or aggregation of the other with nothing new
Different incentive structure	Different funding, ownership or interest in the outcome	Both are paid by, or invested in, the party the claim favours

Collapse each failing cluster to its single highest-graded member and record what was collapsed — that record is what makes the corroboration auditable.

5 — Judge corroboration and emit the verdict

Count the surviving independent sources. Two or more agreeing → corroborated. Exactly one → single-source: report it as such and route to abstain-or-escalate to decide whether to hold or escalate. Zero → abstain-or-escalate. Surviving sources that disagree → contested: state both positions, say which source is more original and more recent, and do not average them. Never resolve a disagreement by picking the more convenient side.

Output template

Every field is mandatory; independent_sources must equal the number of surviving clusters, and collapsed must list every source removed and why.

{
  "claim": "{one specific sentence with value, unit and date}",
  "sources": [
    {"citation": "{originator, title, date, locator}", "grade": "{A1–F6}", "role": "{primary record | party announcement | independent reporting | literature}"}
  ],
  "collapsed": [
    {"citation": "{source removed}", "failed_test": "{originator | first-hand root | publication event | incentive}", "same_as": "{source it collapsed into}"}
  ],
  "independent_sources": {n},
  "verdict": "{corroborated | single-source | contested | uncorroborated}",
  "rationale": "{which sources survived, on what independent roots, and what remains unresolved}"

Worked example

Illustrative data. Claim: "Company X closed a $3.5 billion Series E at a $61.5 billion post-money valuation in March 2025." Five candidates were gathered and graded:

#	Source	Grade	First-hand root	Outcome
1	SEC Form D filing, 4 March 2025	A1	The filing itself	survives
2	Company X blog post, 3 March 2025	B2	The same round, announced by the same party	collapsed into 1 (originator and incentive tests)
3	Reuters report, 3 March 2025	B2	Company announcement + a named investor interview	survives on the interview (documented exception)
4	Tech portal article, 3 March 2025	C3	Quotes Reuters verbatim	collapsed into 3 (originator test)
5	Newsletter, 5 March 2025	D3	Links to the company blog, adds nothing	collapsed into 1 (publication event test)

Two independent sources survive. The filing and the blog post are one source in two clothes — Company X originated both and both serve its interest — so they collapse to the higher grade (A1). Reuters largely repeats the announcement, but its named investor interview is a separable first-hand element from a different originator with a different incentive, so it counts under the documented exception in step 4, with that reasoning written into rationale. Sources 4 and 5 add zero corroboration despite adding two URLs. Verdict: corroborated, 2 independent sources, best grade A1. Strip the investor interview out of source 3 and everything traces to Company X: 1 surviving source, verdict single-source.

Verification

Before the verdict ships, confirm:

• Each surviving source was walked to its first-hand root, and the roots named in the output are actually different documents.
• Every collapsed source appears in collapsed with the test it failed and the source it merged into — none was dropped silently.
• independent_sources equals the number of surviving clusters, and a count of 1 is reported as single-source rather than rounded up.
• No surviving cluster consists only of parties that gain from the claim being true (incentive test applied, not skipped).
• Where sources disagree, both positions are stated with their grades; no digit or figure was averaged.

Pair with adjacent skills

• rate-source-admiralty — grades each candidate before it counts, and decides which member of a collapsed cluster survives.
• sift-source-check — vets an unfamiliar candidate laterally before it joins the pool.
• grounded-fact-check — verifies the specific value once corroboration establishes the claim.
• abstain-or-escalate — when corroboration fails or the surviving sources conflict.
• Methodology counterpart: methodologies/research-methods/mixed-methods.md — corroboration across evidence types at study scale.

Anti-patterns

• Do not count syndications of one wire story as several sources.
• Do not skip the incentive test. Two favourable analyst notes from firms paid by the same vendor are one source here.
• Do not average Admiralty grades across sources. The scale is ordinal: keep the most reliable letter and report the range.
• Do not force a verdict when sources genuinely disagree. Surface the disagreement with its sources.
• Do not treat volume as independence. Ten agreeing pages that share one root are one confirmation.

Reference

• N. K. Denzin, The Research Act: A Theoretical Introduction to Sociological Methods, 2nd ed. New York: McGraw-Hill, 1978 — the data / investigator / theory / methodological typology; reissued Routledge, 2017, ch. "Strategies of Multiple Triangulation", ISBN 978-1-315-13454-3, doi:10.4324/9781315134543.
• Office of the Director of National Intelligence, Intelligence Community Directive 206: Sourcing Requirements for Disseminated Analytic Products, 22 January 2015 — source reference citations, source descriptors, and source summary statements covering "what sources are meaningfully corroborative or conflicting". https://irp.fas.org/dni/icd/icd-206.pdf