The Sight was a form of magic in the Tortallan Universe. It was different from the magical Gift, though the two were not mutually exclusive. People with the Sight could not cast spells, but depending on the power of their particular Sight, could see a number of things invisible to the normal eye. Two known persons in Tortall possessed the Sight - George Cooper and his daughter, Alianne Crow.
George could use his Sight to tell if he was being lied to, to tell if someone was holding out on him, or to recognize someone as a potential friend or enemy - he knew he had to meet Alanna when she first arrived in Corus because his Sight told him so. Alianne could do a lot more with her Sight, as it was amplified by the power of her mother's Gift. Aly could tell if someone was Gifted or a god, ill, pregnant, or lying, and could see the presence of poison in food and water, discern the tiniest of details, see far into the distance as if it was right in front of her, see clearly in the dark, and see magic, both spells left behind and the type of magical skills someone possessed. Alianne used her Sight in all is aspects to help the raka put Dove on the throne of the Copper Isles in the 460s, HE.
The Sight, as well as the Gift, tended to run in families, though while the Gift required training to use properly, no training was necessary to make use of the Sight.