Translating 'amorce'

Reading an article about "traitement moral" in France I came upon this sentence: "Cette amorce d'une première psychothérapie rationnelle, dans la mesure où elle ne laissait pas de place aux phénomènes inconscients, est restée pratiquement ignorée des historiens..."  Among the various translations for 'amorce' that I have found none seem to work in English. "this beginning of ..." "this stimulus for ..."

In my mind 'traitement moral' was the first rational psychotherapy, not simply the beginning of or stimulus for. Perhaps I simply don't agree with the author, but I do want to be sure that I understand him. Thanks for your consideration. Let me know if you have any questions.

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