The most powerful of the gods were omniscient -- they could see and hear everything that happened in the universe. Whether they could act on it, however, is another matter.

Tantalus, a Greek ruler and ancestor of Agamemnon, attempted to test the omniscience of the gods by chopping up his own son, Pelops, and serving him to the gods in a stew. All of the Olympians saw through the ruse immediately, except for Demeter, who ate Pelops' shoulder. Pelops was restored to life and Hephaestus forged him a new shoulder. Tantalus was sent to the Underworld, neck deep in a pond. The fruit on the tree above him would always lift when he tried to take a bite, and the water below him always receded when he bent to drink. From his name comes the word "tantalize."