Public Interest 114 (Winter 1994), 119–25.

Excerpt:

The world has never had a good definition of liberty, and the American people, just now, are much in need of one.” What Abraham Lincoln said in 1864 about liberty in general can be said today about liberty or (in the words of the First Amendment) freedom of speech: we are very much in need of a good definition.

Online:
National Affairs [pdf]