Skocpol and Somers's 1980 typology of comparative history names two of the vault's three bridge poles — 'parallel demonstration of theory' and 'macro-causal analysis'

philosophy-of-sciencecomparative-historymethodologycross-domain-bridgebridge-noteargument-from-silencestructural-equivalence

Theda Skocpol and Margaret Somers's methodological paper distinguishes three "logics-in-use" of comparative history: "Notwithstanding such attempts at homogenization, there are, in fact, at least three distinct logics-in-use of comparative history. One of them, which we shall label comparative history as macro-causal analysis, actually does resemble multivariate hypothesis-testing. But in addition there are two other major types: comparative history as the parallel demonstration of theory; and comparative history as the contrast of contexts." Two of the three map cleanly onto the poles of the vault's own bridge-grading spectrum, and they do so from a single source — which is why the mapping counts as external corroboration rather than coincidence.

Parallel demonstration of theory applies one explanatory framework across historically unconnected cases (the paper's exemplars are Eisenstadt's The Political Systems of Empires and Paige's Agrarian Revolution) specifically to show the framework's reach, not to claim the cases share a history. This is the closest documented analogue to the vault's method-shared-referent-unshared middle category, observation-brooks-dreyfus-forgetting-bridge-is-method-level-not-mechanism-level: one analytic apparatus proving itself repeatable across unconnected material.

Macro-causal analysis is the type built for cases that are causally or historically linked — the pole observation-puckette-dataflow-claims-confirmed-bridge-not-false-friend occupies (premise and conclusion of one argument in one document). Skocpol and Somers, on Barrington Moore's Social Origins of Dictatorship and Democracy: "Macro-analytic comparative historians proceed by selecting or referring to aspects of historical cases in order to set up approximations to controlled comparisons." Cases are read against each other to isolate a cause, not alongside each other to show a theory holds.

The mapping does not extend to the third type. "Contrast of contexts" compares cases to highlight their differences under a chosen frame — not the same operation as the vault's false-friend pole (observation-hawks-jeffress-cosine-pairing-is-embedding-false-friend), which is accidental surface echo with no shared method at all. Two poles line up; the third does not. See moc-argument-from-silence for the grading spectrum this feeds.

Neither match is exact: Skocpol and Somers describe a single scholar deliberately choosing cases to make one persuasive argument, while the vault's bridges are two separate, independently motivated investigations that merely happen to share a method — an assumption gap the observation note observation-vaults-in-between-bridge-category-not-exactly-named-by-located-literature takes up.