In the discussion on bravery in Eth. Eud., III, 1 Aristotle determines the objects that are absolutely dreadful by means of an explicit reference to ‘human nature’. This reference has not received much consideration from scholars in the field. The present paper argues that the reference under discussion entails a notion of ‘human nature’ that corresponds to a human being’s psychological disposition to endure fearful emotions – that is to say, painful emotions that imply the representation of a pain capable of destroying a human being – up to a certain degree of intensity. Furthermore, this article claims that the same notion of ‘human nature’ is implied in Eth. Eud., II, 8 in the discussion of involuntariness concerning the cases of mixed actions where Aristotle refers to the ‘nature’ of the agent as a criterion to determine the involuntariness of an action.