Freedom of thought

Freedom of thought means a person can hold or consider any fact, viewpoint, or thought without being influenced by what others think. This liberty is the foundation from which other freedoms—like freedom of religion, speech, and expression—grow. Although it often precedes these other rights, freedom of thought does not depend on them to exist. Simply declaring a freedom or right does not automatically make it legal or protected; that requires specific legal or philosophical backing. The concept is central to Western societies, and nearly all democratic constitutions safeguard it.

For example, the First Amendment of the U.S. Bill of Rights forbids laws that interfere with religion or prohibit its free exercise. In the 1937 case *Palko v. Connecticut*, Supreme Court Justice Benjamin Cardozo described freedom of thought as “the matrix, the indispensable condition, of nearly every other form of freedom,” noting that this truth has been broadly recognized in American history, with rare exceptions.

Internationally, freedom of thought is enshrined in human rights law. Article 18 of the Universal Declaration of Human Rights (UDHR), which is binding on states that have signed the International Covenant on Civil and Political Rights (ICCPR), grants everyone the right to freedom of thought, conscience, and religion. This includes the right to change one’s religion or belief and to manifest it publicly or privately. The United Nations Human Rights Committee clarifies that this article separates the freedom of thought and conscience from the freedom to manifest a belief, and it permits no limitations whatsoever on the freedom to hold or adopt a religion or belief—these freedoms are unconditional. Similarly, Article 19 of the UDHR guarantees the right to hold opinions without interference. Article 9 of the European Convention on Human Rights also states that everyone has the right to freedom of thought, conscience, and religion.

Historically, suppressing thought is difficult because no one can be certain what another person is thinking. The Bible develops this idea, especially in the writings of Saul of Tarsus, who asked, “For why should my freedom be judged by another’s conscience?” (1 Corinthians 10:29). While Greek philosophers Plato and Socrates touched on freedom of thought only lightly, the edicts of King Ashoka from the 3rd century BC are considered the first decree to respect freedom of conscience. In European tradition, aside from Constantine I’s decree of religious toleration at Milan in 313, major proponents of freedom of conscience (or “soul liberty,” as Roger Williams called it) include Themistius, Michel de Montaigne, Baruch Spinoza, John Locke, Voltaire, Alexandre Vinet, John Stuart Mill, and theologians Roger Williams and Samuel Rutherford.

Queen Elizabeth I revoked a thought censorship law in the late sixteenth century because, according to Sir Francis Bacon, she did “not like to make windows into men’s souls and secret thoughts.” Yet during her reign, Giordano Bruno published books that raised controversial topics banned by the Catholic Church, such as the possibility of an infinite universe. Refusing to recant, Bruno was burned as a heretic by the Italian Inquisition in Rome, becoming a martyr for free thought. Oliver Cromwell, according to Ignaz von Döllinger, was the first major world figure to establish and enforce the principle of liberty of conscience and the rejection of religious coercion.

Freedom of expression can be limited through censorship, arrests, book burning, or propaganda, which in turn discourages freedom of thought. Examples of effective campaigns against free expression include the Soviet Union’s suppression of genetics research in favor of Lysenkoism, Nazi Germany’s book-burning campaigns, the radical anti-intellectualism enforced in Cambodia under Pol Pot and in Nazi Germany under Adolf Hitler, strict limits on expression in Communist China and Cuba, and similar restrictions under capitalist dictatorships such as Augusto Pinochet’s Chile and Francisco Franco’s Spain.

The Sapir–Whorf hypothesis suggests that thought can be embedded in language, implying that limiting language use is a form of restricting freedom of thought. George Orwell explored this in his novel *1984* through the concept of Newspeak, a stripped-down English that lacked capacity for metaphor and limited original ideas. More recently, neuroimaging technology has raised concerns about the possibility of reading and suppressing thought, giving rise to the fields of neuroethics and neuroprivacy. Humanists International publishes an annual Freedom of Thought Report that compiles country-by-country data on this topic.