In a small heavy-bottomed pot dissolve the sugar in the corn syrup and water. Bring to a boil. Boil to thread stage (the candy thermometer should read between 223 to 234 degrees F). Brush down the inner wall of the pot with a heat-proof pastry brush and a small amount of water to prevent crystal formation.
In the meantime beat egg whites with mixer and whisk attachment until they hold stiff but not dry peaks. Pour 2/3 of the boiled syrup mixture in a thin stream over the beaten egg whites, whisking all the time on high speed. Put the remaining mixture back on the heat and cook to soft ball stage (the candy thermometer should read between 234 to 240 degrees F). Whisk into the egg white mixture with the mixer on high speed. Add extract. Continue whisking until mixture forms stiff peaks.
Pour into a buttered 9 by 13-inch pan. Let cool and cut. Store in an airtight container for chewier divinity or leave uncovered for a crispier texture.