Darkness, no matter how ominous and intimidating, is not a thing or force: it is merely the absence of light. So light need not combat and overpower darkness in order to displace it — where light is, darkness is not. A thimbleful of light will therefore banish a roomful of darkness.

The same is true of good and evil: evil is not a thing or force, but merely the absence or concealment of good. One need not "defeat" the evil in the world; one need only bring to light its inherent goodness.

From the teachings of the Lubavitcher Rebbe