Cite as: 575 U. S. ____ (2015) 15 Opinion of the Court because he lacked the knowledge that the materials were legally obscene “would permit the defendant to avoid prosecution by simply claiming that he had not brushed up on the law.” Id., at 123. It was instead enough for liability that “a defendant had knowledge of the contents of the materials he distributed, and that he knew the character and nature of the materials.” Ibid. This holding does not help the Government. In fact, the Court in Hamling approved a state court’s conclusion that requiring a defendant to know the character of the material incorporated a “vital element of scienter” so that “not innocent but calculated purveyance of filth . . . is exorcised.” Id., at 122 (quoting Mishkin v. New York, 383 U. S. 502, 510 (1966); internal quotation marks omitted). In this case, “calculated purveyance” of a threat would require that Elonis know the threatening nature of his communication. Put simply, the mental state requirement the Court approved in Hamling turns on whether a defendant knew the character of what was sent, not simply its contents and context. Contrary to the dissent’s suggestion, see post, at 4–5, 9– 10 (opinion of THOMAS, J.), nothing in Rosen v. United States, 161 U. S. 29 (1896), undermines this reading. The defendant’s contention in Rosen was that his indictment for mailing obscene material was invalid because it did not allege that he was aware of the contents of the mailing. Id., at 31–33. That is not at issue here; there is no dispute that Elonis knew the words he communicated. The defendant also argued that he could not be convicted of mailing obscene material if he did not know that the material “could be properly or justly characterized as obscene.” Id., at 41. The Court correctly rejected this “ignorance of the law” defense; no such contention is at issue here. See supra, at 10.