Books V, VI and VII of the Nicomachean Ethics are word for word identical to Books IV, V and VI of Aristotle's other ethical treatise, the Eudemian Ethics. Wikipedia's own background section names two competing explanations still in circulation: that three books were lost from the Nicomachean Ethics and replaced with the parallel Eudemian material, or that an editor rather than Aristotle himself gave both works their current shape, without resolving between them.
What would resolve this A manuscript tradition or independent ancient testimony establishing which treatise originally contained the shared material, or a stylistic analysis accepted across Aristotle scholarship, would settle which work the common books belong to.
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