Faced with a rule the Buddha himself had left undefined, the elder Mahakassapa, presiding over the First Council, chose the option that changed the least. His ruling held that because the exact boundary of the lesser and minor rules could not now be determined with confidence, the order should neither lay down anything new nor abolish anything that had already been established; the full body of training rules, whatever their relative weight, would stand as a single, undivided whole. His own stated reasoning, preserved in the Cullavagga, was practical as much as doctrinal: if the community relaxed its discipline immediately after the Teacher's death, outsiders would say the rules had only ever been kept while he was alive to enforce them, discrediting the entire monastic project at the moment it could least afford it.
The Council accepted the ruling, and its consequences reached well past that one meeting. By refusing to prune the rules even where the Buddha had explicitly allowed it, Mahakassapa's decision fixed the Vinaya in the comprehensive form later tradition would inherit, rather than leaving it open to selective revision by each following generation. Scholars who study the parallel accounts preserved across multiple early Buddhist schools note that this outcome, not the abolition option some monks reportedly favored, is what every surviving version of the story agrees actually happened, which is part of why the episode is treated as a real hinge in the Vinaya's early transmission rather than a purely legendary embellishment.