His most famous view on the 1st amendment was that it did not protect people that falsely yelled "fire" in a crowded theater causing harm to the public.
Holmes believed that people have a natural impulse toward censorship. Government is especially prone to attempt censorship. Therefore, the First Amendment is critical to protecting the right to dissenting thought.
He would test government's right to limit speech by whether the words "create a clear and present danger [so as to] bring about ... substantive evils." Schenck v. United States.
