Homer's two central heroes, Odysseus and Achilles, are in many ways differing manifestations of the same themes. While Achilles' character is almost utterly consistent in his rage, pride, and near divinity, Odysseus' character is difficult to pin down to a single moral; though perhaps more human than Achilles, he remains more difficult to understand. Nevertheless, both heroes are defined not by their appearances, nor by the impressions they leave upon the minds of those around them, nor even so much by the words they speak, but almost entirely by their actions. Action is what drives the plot of both the Iliad and the Odyssey, and action is what holds the characters together. In this respect, the theme of humanity is revealed in both Odysseus and Achilles: man is a combination of his will, his actions, and his relationship to the divine. This blend allows Homer to divulge all that is human in his characters, and all that is a vehicle for the idyllic aspects of ancient Greek society. Accordingly, the apparent inconsistencies in the characterization of Odysseus can be accounted for by his spiritual distance from the god-like Achilles; Achilles is more coherent because he is the son of a god. This is not to say that Achilles is not at times petty or unimaginative, but that his standards of action are merely more continuous through time. Nevertheless, both of Homer's heroes embody important and admirable facets of ancient Greek culture, though they fracture in the ways they are represented.
Odysseus is a peculiar mix of both heroic and intelligent qualities that make him seem both human and supernatural. The Odysseus portrayed in the Iliad somewhat contrasts the Odysseus we see in the Odyssey. For the purposes of the former, he is represented as a man of conviction, possessing significant military genius and guile, as well as persuasive capabilities. In the latter, however, some of his more ignoble traits are revealed: he is a braggart, he almost dishonorably uses poisoned arrows, and he shows conceit in his victory over the Cyclops. It is sometimes difficult to reconcile this man with the one who willingly gives up eternal life for the moral condition and the chance to return to his wife. Largely, the problems with understanding the moral position of Odysseus stem from his immense experience and cleverness, which make him at once mortal and fantastic.
Achilles, on the other hand, can almost be fully comprehended from his initial disagreement with Agamemnon. Agamemnon's unreasonable actions seem to justify Achilles' refusal to engage his men in battle, primarily, because his pride will not allow him to act. Achilles believes himself to be the most important man in the army and the injury cannot be forgiven. Even when a diplomatic escape is contrived by Agamemnon, Achilles sees his position as unchanged-doubtlessly, Odysseus would have relented but Achilles is unable to forget past grievances.