393 U.S. 97 (1968)
In 1928 Arkansas voters adopted Initiated Act No. 1.1 This law made it a misdemeanor for any teacher in a state-supported school or university to teach the theory that mankind ascended or descended from a lower order of animals.2 It also prohibited adopting or using a textbook that teaches that theory.3 Violators were subject to dismissal from their positions.4
For the 1965-1966 academic year the Little Rock school administration adopted a new textbook for tenth-grade biology.5 The administration followed the recommendation of its biology teachers.6 The textbook contained a chapter setting forth the Darwinian theory of the origin of man from a lower form of animal.7
Susan Epperson had graduated from the Arkansas school system.8 She later earned a master's degree in zoology from the University of Illinois.9 She was hired in the fall of 1964 to teach tenth-grade biology at Central High School in Little Rock.10 She was assigned to use the new textbook.11
Epperson filed suit in the Chancery Court of Arkansas.12 She sought a declaratory judgment that the statute was void.13 She also sought an injunction preventing state and local officials from dismissing her for using the textbook.14 H. H. Blanchard, a parent of children in the public schools, intervened in support of the action.15 The Chancery Court held the statute unconstitutional under the Fourteenth Amendment.16
On appeal the Supreme Court of Arkansas reversed.17 It issued a two-sentence per curiam opinion.18 The opinion upheld the statute as a valid exercise of the state's power to prescribe the public-school curriculum.19 It expressed no opinion on whether the Act prohibited any explanation of evolution or only the teaching that the theory is true.20 Epperson prosecuted an appeal as of right to the United States Supreme Court under 28 U.S.C. § 1257(2).21
At the time of the appeal only Arkansas and Mississippi still had anti-evolution statutes on their books.22 The record contained no evidence of any prosecution ever having been brought under the Arkansas law.23
Whether Arkansas' 1928 anti-evolution statute is unconstitutionally vague under the Due Process Clause of the Fourteenth Amendment?24
No. The Court declined to rest its decision on vagueness grounds.27 The Arkansas Supreme Court expressed no opinion on whether the Act prohibits any explanation of the theory of evolution or merely forbids teaching that the theory is true.28 Counsel for the State represented that the statute would criminalize making students aware of the theory at all.29 The Court observed that on either possible interpretation the statute must fall for establishment reasons rather than vagueness.30
The Court did not invalidate the statute on vagueness grounds and instead resolved the case under the First Amendment.31
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Justice Black would have struck down the statute solely on vagueness grounds to avoid deciding sensitive curriculum questions.32 He noted that the Arkansas Supreme Court had deliberately refused to clarify whether the Act banned all mention of Darwin's theory or only assertions of its truth.33 This left teachers unable to know when they violated the law.34
He argued that resolving the case on vagueness would respect state authority to set curricula without reaching the broader Establishment Clause issue.35
Justice Stewart concurred in the result on vagueness grounds alone.36 Because the Arkansas Supreme Court left open whether the statute forbade any mention of the theory, the law was too vague to stand under the Fourteenth Amendment.37
He emphasized that no state could constitutionally forbid a teacher to mention Darwin's theory at all.38
Whether the Arkansas statute violates the First Amendment's prohibition on laws respecting an establishment of religion or prohibiting the free exercise of religion, as made applicable to the states by the Fourteenth Amendment?39
Government must remain neutral in matters of religious theory, doctrine, and practice.40 It may neither aid nor oppose any religion or religious theory.41 If the purpose or primary effect of a law is the advancement or inhibition of religion, the enactment exceeds the scope of legislative power under the First Amendment.42
Yes. Arkansas adopted the statute to prevent teachers from discussing the theory of evolution because that theory conflicted with the belief of some citizens that the Book of Genesis supplies the exclusive doctrine on the origin of man.43 The law selected a particular segment of scientific knowledge and proscribed it solely because it was deemed to conflict with a particular religious doctrine rather than for any secular educational reason.44 The statute's predecessor in Tennessee had explicitly targeted theories denying the divine creation story.45 Arkansas's version pursued the identical objective through less explicit language.46
The State made no attempt to remove all discussion of human origins from the curriculum.47 Instead it targeted only the evolutionary account because of its supposed clash with a literal reading of the Bible.48
The Arkansas statute violates the First Amendment as incorporated by the Fourteenth Amendment.49
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Justice Harlan joined the Court's holding that the statute constitutes an establishment of religion forbidden to the States.50 He criticized the Arkansas Supreme Court's opaque opinion as an improper effort to avoid confronting the constitutional question and to shift responsibility to the federal courts.51 He agreed that once the constitutional claims had been properly raised and decided below, this Court could not avoid resolution.52
He viewed the state court's handling of the case as a studied effort to pass the buck to the federal judiciary.53
Justice Black expressed doubt that the statute was motivated by a desire to enforce a particular religious view.54 He suggested the people of Arkansas may simply have wished to remove a controversial subject from the schools.55 He questioned whether forbidding discussion of evolution while omitting literal Biblical creation actually places the State in a position of religious neutrality.56
He warned that the Court's approach risked infringing the religious freedom of those who view evolution as anti-religious.57 He also doubted that a teacher possesses a constitutional right to teach subjects the school managers do not want discussed.58
Justice Stewart concurred only in the result.59 The Arkansas Supreme Court had left the statute's scope open on whether the Act prohibited any explanation of the theory or merely teaching that it is true. Stewart concluded that the law was unconstitutionally vague under the Fourteenth Amendment. He would not reach the broader establishment question.60