In the Odyssey, what motivates Odysseus to dress as a beggar?

The answer

Odysseus dresses as a beggar for one overriding strategic reason: concealment enables reconnaissance and revenge. After twenty years away, he cannot simply march into his hall and announce himself. More than a hundred suitors have occupied his home, courted his wife Penelope, and drained his wealth. If they knew the true king had returned, they would either flee or, more likely, kill him on the spot before he could act. The beggar disguise (given to him by Athena, who ages his skin, dims his eyes, and dresses him in rags) lets him move invisibly through his own household.

The disguise serves several linked goals. First, it lets Odysseus gather intelligence: he watches the suitors' arrogance firsthand, counts their number, and studies the layout of the hall. Second, it lets him test loyalty. He sees that the swineherd Eumaeus and the cowherd Philoetius remain faithful, while the goatherd Melanthius and the maid Melantho side with the suitors. His old dog Argos recognizes him and dies; his nurse Eurycleia knows him by the scar on his thigh. These tests tell him exactly who will stand with him. Third, the disguise buys him time and surprise, the two things a lone man needs against a crowd.

How we know: Amphimedon's account

The clearest confirmation comes from an unexpected voice. In Book 24, the ghost of the suitor Amphimedon, now dead, describes the whole plot from the losers' point of view in the underworld. He recounts how Odysseus returned in disguise, how Penelope set up the contest of the bow, and how the beggar strung it and turned it on them. Amphimedon's speech is essentially the suitors admitting they were outmaneuvered by a plan they never saw coming. That the deception is narrated by its victims underscores its purpose: it worked precisely because no one recognized the king until it was too late.

Why the disguise, not a direct fight

A reader might ask why Odysseus does not simply reveal himself and rally loyal men. The Odyssey answers this through the theme of metis, cunning intelligence, which is Odysseus's defining trait. Throughout the epic he wins by wit, not brute force: the Trojan Horse, the escape from the Cyclops as "Nobody," the navigation past Scylla. The beggar disguise is another expression of that intelligence. It also lets Athena stage-manage events, and it sets up the emotional payoff of the recognition scenes with Telemachus, Eurycleia, and finally Penelope.

The beggar's low status matters too. As a beggar he is beneath notice, which lets the suitors reveal their true cruelty (Antinous throws a stool at him). Their mistreatment of a helpless stranger violates xenia, the sacred law of hospitality, and morally justifies the slaughter that follows. So the disguise is not only tactical but thematic: it exposes the suitors' guilt before it seals their doom.