海神波塞冬与智慧女神女战神雅典娜竞争上岗雅典保护神。波塞冬送给雅典象征胜利的白马，雅典娜则给象征和平的橄榄枝。于是雅典人选择了和平。这是个广为流传的故事，但我现在想不起来最初出处。海神波塞冬与雅典娜争当雅典保护神时，克罗普斯(Cecrops)是见证人。

公元1世纪罗马帝国时代奥维德的《变形记》第六卷中提到这个故事(TheMetamorphoses translated by Horace Gregory)，但没有白马，只有海水。

The God of Ocean stuck the rock-grown cliff

With his long trident where salt water gushed

Toname the place his own; Pallas herself

Headcased in helmet, and aegis at her breast

These to defend her while her spear pierced earth

Downwhere a silver-glancing olive free

Shotup heavy with olives on its boughs;

Athena’s victory while the high gods marveled!

公元2或3世纪的The Library of GreekMythology也有类似的故事，我手里的英译本是第3卷第11章。但多些细节，而且与传统故事有一点儿差异，虽然更早的传统故事我也没有读过。

So Poseidon was the first to come to Attica, and striking a blow with his trident on the middle of the Acropolis, he caused a sea to appear, which is now known as the Erechtheid Sea. After Poseidon, Athena arrived; and taking Cecrops as her witness, she claimed possession by planting an olive tree, which is still shown to visitors in the Pandroseion. When the two of them entered into conflict for Posscssion of the land, Zeus separated them, and appointed as judges, not Cecrops and Cranaos as some have claimed, not Erysichthon, but the twelve goods. In accordance with their decision, the country was awarded to Athena, because Cecrops had testified that it was she who had first planted the olive tree. So Athene named the city Athens after herself while Poscidon, in a rage, flooded the Thriasian plain and submerged Attica under the sea.

这个说法仍有点小问题。那12神是不是包括雅典娜和波塞冬？如果不包括，数目就不对了。如果包括，他们本来是争讼的两造。