These are some notices about my personal research on the connection between Epicurean philosophy and its reception by Marx. Don't take them too seriously.
Some years ago I discovered an interesting connection between Marx and Epicurus. I had read the verses of Lucretius on cultural evolution and suddenly I reminded what is so called "historical materialism". I had to laugh out loud because I thought perhaps Communism might evolve only some steps further. I did so, because I reminded that Marx completed his Dissertation in March 1841 about "The Difference Between the Democritean and Epicurean Philosophy of Nature". It's quite interesting because De Rerum Natura is perhaps the only book from classical antiquity, trying to compare some elements of Democritean and Epicurean philosophy. For sure, Lucretius had to be one of Marx's most important resources.
This was just the start of my reserach about the connection between Marx and Epicurean philosophy. Just a funny fact and it seemed to be just a remindable similarity.
I wasn't able to forget about the topic, so I checked some years later Marx's dissertation. And I really wondered about, because Marx's refers in his dissertations introduction to the letter to Menoikeus:
"Philosophy, as long as a drop of blood shall pulse in its world-subduing and absolutely free heart, will never grow tired of answering its adversaries with the cry of Epicurus:
Not the man who denies the gods worshipped by the multitude, but he who affirms of the gods what the multitude believes about them, is truly impious."
This passage gives several information: First: Marx knowed the letter to Menoikeus. Second: He also refers to in matter of critique of religion. Third: We should not underestimate the influence of Epicurus on Marx (especially, because Marx also did reserach on hellenistic philosophy in his youth).
The whole topic is so interesting to me, because the philosopher Ludwig Feuerbach is always said to have had influenced Marx heavenly. Heavenly in kind of critique of religion and heavenly in kind of materialism. Ironically, his basic work "The Essence of Christianity" was published also in 1841, perhaps some months later than Marx' dissertation. My conclusion is, perhaps, just perhaps, you could forget about Feuerbach. Marx didn't need Feuerbach.
I know little about Marx and I know little about Feuerbach. I know nothing about their personal connection. These are the points I have to evolve my knowledge. Unfortunately, there is rare primary literature on the topic. Just cultural scientists and marxists copying from each other.
At the moment, my hypothesis is the following: Marx was heavenly influenced (from several sources and) by Epicurus, from which he borrowed some key ideas. Later, writers like Feuerbach also did influence Marx, but perhaps they rather served as a mirror to Marx. Feuerbach was a compagnon in the same era. Feuerbach was a person to refer to and to talk with. Who would refer to Epicurus, this old philosopher? We also have to remind that in the 19th century Epicurus was just available to an elite who was able to handle classic Latin and Greek.
If there might have been a great influence of Epicurean philosophy on Marx, this influence logically might been overwritten by the living philosophers of that era.
Finally, I would like to share a sweet piece of chocolate with you. Erich Fromm mentions the mentioned quote by Epicurus in his book "Marx's Concept of Man" but without mentioning Epicurus. He handles this quote just global, as a sign of Marx's refering to classical antiquity philosophers. He lists every other philosopher... but not the one.