Justice Potter Stewart, in his concurrence to the majority opinion, created the standard whereby all speech is protected except for "hard-core pornography". As for what, exactly, constitutes hard-core pornography, Stewart said "I shall not today attempt further to define the kinds of material I understand to be embraced within that shorthand description, and perhaps I could never succeed in intelligibly doing so.
Justice Potter Stewart, in his concurring opinion, established a standard for free speech protection. However, he refused to define what constitutes "hard-core pornography," stating that it was too difficult to articulate clearly.