"Sunlight,” as has so often been observed, “is the most powerful of all disinfectants.”

Justice Brandeis' 1964 ruling referring to this passage:

The conscience and common sense of the nation as a whole keep down the evils which have crept into the working of the Constitution, and may in time extinguish them. Public opinion is a sort of atmosphere, fresh, keen, and full of sunlight, like that of the American cities, and this sunlight kills many of those noxious germs which are hatched where politicians congregate. That which, varying a once famous phrase, we may call the genius of universal publicity, has some disagreeable results, but the wholesome ones are greater and more numerous. Selfishness, injustice, cruelty, tricks, and jobs of all sorts shun the light; to expose them is to defeat them. No serious evils, no rankling sore in the body politic, can remain long concealed, and when disclosed, it is half destroyed.

-James Bryce (The American Commonwealth)