Cover of Censoring Sexuality, part of the Manifestos for the 21st Century series“Wherever they burn books,” wrote Heinrich Heine in 1823, “they will end up burning people.” Predictably, Heine was one of the writers whose books were flung into the flames by the SA in Berlin a little over a century later, along with those by Marx, Freud, Maxim Gorky, Stefan Zweig and many others. As these four short books on censorship – of the word, the body, the moving image and sexuality – make clear, freedom of expression in all its forms has always been deeply threatening, not only to totalitarian regimes, but to society itself. But fashions change and it is precisely these constantly shifting and evolving forms of perceived threat that make this series, subtitled rather portentously Manifestos for the 21st Century, so fascinating.

The history of the written word, writes Julian Petley, is in fact punctuated by repeated attempts to curb writers. In their time, many of the people we now regard as the most influential thinkers were banned, whether by the Roman Catholic Church and its various Indexes, which suppressed Boccaccio and Rabelais in an attempt to “expurge from human memory the names of heretics”, or by any number of successive rulers and governments. And as the standards of taste and imagined danger have changed, so has the nature of those banned. For 19th-century France, it was Flaubert and Balzac who seemed to pose the greatest danger to a stable and moral society.

Just as the need to keep writers from disrupting the public has preoccupied governments, so has the whole idea of the power of the written word exercised philosophers. People, argued Milton, are perfectly capable of distinguishing right from wrong, provided they are given unlimited access to the ideas and thoughts of those whose words enable them to do so. “Books, promiscuously read” and the freedom to “scout into the regions of sin and falsity” alone allow people to acquire true virtue and knowledge. But even those who argued that the liberty to hear and say things was crucial to the health of nations did not regard that liberty as absolute. Milton himself specifically excluded Roman Catholics from being allowed to express themselves freely because he regarded Catholicism as idolatry, “priestly dogmatism under the cloak of religion”.

Censorship has played no less a role in shaping the course of movie history. Even before the Lumière brothers projected their first films in 1895, police in Atlantic City had cracked down on erotic peep shows. In 1896, a tender kiss between two ageing stars of a Broadway play, captured on 50 feet of film, outraged the public to such an extent that there were calls for it to be banned. Thus began a long battle between film-makers and clergymen, judges and moralists who argued that cinema is a major influence on juvenile crime, promiscuity and violence. This, suggests Julian Petley, may originally have been to do with the size and immediacy of film, the fact that it took audiences to strange settings, that it invited them to fantasise, that it was popular with the working classes and that cinemas themselves were regarded as unsanitary and dangerous places.

By the Second World War, censorship boards were laying down rules to cover “degrading exhibitions of animal passion”, “marital infidelity” and the lampooning of monarchy and army officers. Audiences were regarded as untrustworthy children and it was with considerable pride that the British Board of Film Censors was able to announce in 1937 that there was “not a single film showing in London today which deals with any of the burning issues of the day”.

The banning of images of the human form has followed a longer and somewhat different course, one marked by a real reluctance to represent the body in a straightforward way. The young maidens of Archaic Greece had distinctly boyish shapes, while Christianity emerging from the Middle Ages struggled to reconcile a fixation with original sin and the need to portray martyred saints in their semi-nude forms. After Michelangelo’s death, the naked figures in the Sistine Chapel had their genitals tastefully covered when people complained that such images were more suited to the bath house than the chapel. When, in the 19th century, the French painter Gerome painted naked young women, he placed them safely in Middle Eastern slave markets (but gave them no pubic hair), where they could be pitied and moralised over and yet enjoyed. As Edward Lucie-Smith writes, the history of art is also a story of the representation of the human body being censored to suit the ideological purpose of the day. Images of the body, he suggests, have to be edited, because they present a continuing source of anxiety to those who view them.

Paul Bailey’s beautifully written and eloquent essay on censoring sexuality is different again. It is cast both as his own personal story of growing up gay in a world hostile to all but heterosexual relationships and as an account of some of the more remarkable of the 20th-century men – Proust, Mikhail Alexeyevich Kuzmin, Francis Bacon – who defied such conventions. His essay ends with a series of short “documents”, reminders of the persecution suffered today in Egypt, Morocco and Iran, where not long ago two men were hanged in Erin Prison for being gay. Gay men and women, writes Bailey, tend to this day to be defined by what is least interesting in their characters, their gayness, “an unthinking censorship of their essential humanity”. The real risks are not harmless sexual adventures, but “pride and cruelty... the causes of war, the source of ignorance, the dismantlers of all that we need to honour in our hearts, minds and souls.”

That true human rights cannot exist without freedom of expression has long been acknowledged. From Jefferson to Tom Paine, from Eleanor Roosevelt to countless successive declarations, acts and covenants, the liberty to express oneself without molestation has been repeatedly upheld. These four essays, succinct and enjoyable surveys of past and present intransigence, bear witness to the many evils of censorship. They touch, but perhaps dwell too little, however, on modern times, when the internet, the mobile phone and ever more creative technology have effectively created a world in which total censorship, even of issues widely acknowledged as being inherently harmful to modern society – hate speech, child pornography, the depiction of extreme violence and abuse – is no longer possible anywhere. The question becomes: how and to what extent this material should, and can, be banned.

“Free speech does not mean free speech,” announced the Law Lords in 1936; “it means speech hedged in by all the laws against blasphemy, sedition and so forth.” That the press, books, films and art must all have the right to impart information and ideas is beyond question. But the public has rights too, and these include those of not being offended, shocked, disturbed or even endangered. It is the balance between the two that is so hard to find.

Manifestos for the 21st Century are published by Seagull Books