Werbos's DOCSUB episode entered the public record 7–12 years after RHW's 1986 Nature paper, foreclosing a causal reading

werbosrumelhartbackpropagationcitation-historydocsubhistory-of-mlchronologybridge-check

Rumelhart, Hinton and Williams's "Learning representations by back-propagating errors" appeared in Nature 323:533–536 on 1986-10-09 (established at Tier 1 in claim-rhw-1986-reference-list-four-works). Werbos's account of DARPA keeping his DARPA-funded report out of DOCSUB — see claim-werbos-1978-docsub-blocked — comes from an oral-history interview whose own transcript header reads "June 1993, Baltimore, Maryland," first published in Talking Nets: An Oral History of Neural Networks (MIT Press, 1998).

That leaves a gap of roughly seven years between the Nature paper's publication and the earliest located telling of the DOCSUB episode, and about twelve years to its earliest located appearance in print. Rumelhart, Hinton and Williams could not have shaped their 1986 reference list in reaction to a story that, on the record as searched, was not circulating in any retrievable public form until 1993.

The "earliest located" is load-bearing and is an argument from silence (see moc-argument-from-silence): no pre-1986 telling of the DOCSUB episode has been found in three vault sessions, but Werbos published prolifically in the 1970s and 1980s and no systematic search of that corpus for an earlier mention has been run. The 1993 dateline is therefore a ceiling on the documented record, not a proof that the story was untellable before it.

This is a narrow, chronology-only claim, and it forecloses less than it first appears. What the dates rule out is the reading in which RHW's short reference list is a response to — or is explained by the field's knowledge of — the DOCSUB narrative: that narrative was not available to respond to. They do not rule out the suppression itself (c. 1978) having made Werbos's work harder to find by 1986; that broader reading is what claim-werbos-docsub-report-and-rhws-missing-1974-thesis-are-different-documents addresses, by showing the blocked document and the uncited document are not the same text. Neither claim addresses why the gap exists at all. See claim-rhw-1986-reference-list-four-works for Hinton's own explanation of the gap (genuine ignorance of the history, not suppression by anyone).