Came across a weird thread on /leftypol/ a while back where a user claimed that Max Stirner/Johann Caspar Schmidt was not a real person. They argued that Max was instead created by Engels as a pseudonym to promote ideas Engels held but did not feel comfortable expressing publicly. Partially due to wanting to avoid straining his relations with Marx, and perhaps in hope of bringing Marx around to his point of view and persuading him and others that egoist ideas were fairly compatible with communism.
They offered as evidence that little or nothing is known about Stirner, that much of what we do know (including the only known depictions of his appearance) come via Frederich Engels, that elements of his philosophy are similar to opinions held by Engels earlier in life, a lack of governmental documentation related to Stirner, and some irregularities with his grave that I cannot recall.
I know little about the ins and outs of German philosophical circles during the relevant time frame, so I have to ask: is there any merit to this claim, or is it utter bunk?
I am honestly a bit at a loss of how to respond to that claim. It is not like the only source for Stirner's existence is German Ideology and his own works. Contemporaries wrote about him, Bruno Bauer for example. And just from a timing standpoint, Marx and Engels only began to collaborate closely in 1845, which is a year after Stirner finished his most famous work , The Ego and its Own, to say nothing of all the other works he wrote before then.
Stirner (real name Johann Kaspar Schmidt) himself died young and was not as influential as Marx, Proudhon, Bakunin or some of the other more famous radical thinkers in his own day, and even when he came into some prominence at the end of the nineteenth century it was among fairly narrow groups (the budding individualist tradition, maybe Nietzche, existentialists, etc), it never had the all encompassing reach of Marx, so it makes sense that there was not the fervent collecting and compiling of his works that there was with Marx (Armand notes that the first real biography of him was published in 1897). This makes it more difficult to do casual research on him, but to go from that to "e did not exist" is just bizarre.
Biographical details are from Guerrin's anthology No Gods, No Masters, which includes a brief biographical sketch by turn of the century anarchist thinker Emile Armand.