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's concurring opinion in a case concerning obscenity law created a standard for free speech that protects all speech except for what he deemed to be "hard-core pornography." He declined to define this category, acknowledging its complexity and the difficulty of articulating it clearly.