This week, Donald Trump posted an AI image of himself dressed in white robes, placing a glowing hand over an ill or deceased man in a hospital bed, as if to heal or resurrect him. The image, posted on Truth Social, was widely taken as him presenting himself as a Messianic Jesus figure.Sometime the next morning, he deleted the post. “I thought it was me as a doctor,” he explained to reporters, according to Time magazine. Jesus? “Only the fake news could come up with that one.” But the post was widely interpreted as blasphemous – including by conservative Catholic group CatholicVote.org.“I don’t know if the President thought he was being funny or if he is under the influence of some substance or what possible explanation he could have for this OUTRAGEOUS blasphemy,” declared Megan Basham, a prominent conservative Protestant Christian writer, on X. “But he needs to take this down immediately and ask for forgiveness from the American people and then from God.”“I was very grateful to see how many conservative Christians immediately denounced the blasphemous Jesus/Trump image,” said pastor Doug Wilson, who recently led a prayer service at the Pentagon and founded the network of churches War Secretary Pete Hegseth belongs to.What is blasphemy?Within the Christian tradition, blasphemy has historically been an unstable, shifting idea. But, simply put, it means speech, thought or action that shows contempt for – or mockery of – God and sacred matters.Judaism and Christianity’s concept of blasphemy came from the injunction in the Old Testament not to revile God. Within the Old Testament, it was treated as a crime, punishable by death: “One who blasphemes the name of the Lord shall be put to death; the whole congregation shall stone the blasphemer.”The New Testament expanded the concept to include the rejection of Jesus. Eventually, cursing, reproaching, challenging, mocking, rejecting or denying Jesus became blasphemous. More particularly, posing as Jesus or asserting powers that belong only to him was considered blasphemous in medieval times. The “Christs” that emerged were treated harshly, as dangerous heretics. This is where Trump’s presentation of himself as Jesus would undoubtedly be considered blasphemous.Broadly, anything said or done that offended believers could be construed as blasphemous. Catholics at the time of the Reformation in the 16th century tended to brand those who offended them as heretics. Protestants generally preferred the term blasphemy for anything they disliked or disagreed with. For example, 16th century theologian Martin Luther – a seminal figure in the Protestant Reformation – condemned as blasphemous not only Catholics, but also Jews and Muslims.Blasphemy as sin or crime James Nayler. Britannica From the 17th century onwards, blasphemy became not so much an offence against God as one against society. Within the unstable societies of early modern Europe, blasphemy was viewed as socially and politically subversive and prosecuted as such. The Quaker James Naylor was imprisoned in 1656 for reenacting Jesus’s entry into Jerusalem on Palm Sunday.Early in the 17th century, blasphemy crossed to the United States. Virginia’s first law code specified death for blaspheming the divine Trinity.Despite the first amendment to the US constitution, protecting free speech, blasphemy laws were regularly enacted. The US Supreme Court didn’t rule that laws against blasphemy infringed the right to free speech until after World War II. Several states still have blasphemy on their books.England’s Blasphemy Act of 1697, which criminalised the denial of the Holy Trinity, the truth of Christianity, or the divine authority of the Bible, carried over into the colonies of Australia and New Zealand.Blasphemy is no longer an offence under Australian federal law, though laws governing it vary across the states: it’s still in the criminal code of many of them. New Zealand’s criminal code deals with “blasphemous libel” as part of “crimes against religion, morality and public welfare”.Is there blasphemy in Islam?Within Islam, there is no exact equivalent to “blasphemy”. But the idea of the “word of infidelity” is analogous to it. In practice, it amounts to mockery of God, the prophet, or the Islamic tradition generally.So, when Trump mockingly declared “Praise be to Allah” in a recent post, he was guilty of blasphemy in Muslim eyes. Conservative commentator Dinesh D'Souza compared it to the Old Testament account of the prophet Elijah, who mocked the prophets of Baal in 1 Kings 18. The Islamic advocacy group Council on American-Islamic Relations called it “disturbing” and “offensive to Muslims”.Laws against blasphemy are actively enforced in many modern Islamic states.Does blasphemy matter?It is not blasphemous to speak or publish opinions that are hostile to Christianity, Judaism or Islam – or for that matter, any religion. What matters is not so much the substance of criticism as the manner in which it is made. We should only worry when criticism becomes a form of “religious hate speech”. The question we should ask is about intent. In a secular society, where we do identify ill intent, we may wish to think about “blasphemy” as a matter of public morality, not theology. So, what about Donald Trump’s post? Does it matter?If we consider “blasphemy” to include the mocking of religion, there is little doubt that Trump’s mockery of Islam is blasphemous. If we believe his deleted Truth Social post was intended to suggest he is Jesus – or in some sense divine – then Christians are entitled to consider him blasphemous. That said, from a secular perspective, it is more self-indulgent foolishness than hate speech – but nonetheless, extremely inappropriate for a US president.Philip C. Almond does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.