At the turn of the 20th century, branches of empirical science were closely linked with studies of the occult and spiritual realm. Scientific breakthroughs like Einstein’s theory of relativity and Freudian psychology, along with the great movement of modernization and industrialization in the West, created a rapidly changing, disorienting world. Life and society as people knew it was altered down to foundational beliefs in the universe and human nature. Increasing access to land and sea travel meant mass migration and increased intermingling of people from different cultures.

Although it is Cthulhu that threatens the human race, and the Cthulhu cultists who menace Thurston’s life, the real threat in “The Call of Cthulhu” is modernity. Lovecraft was socially conservative and, paradoxically, the “mongrel” races who align with the prehistorical Old Ones represent a grotesque vision of the future that Lovecraft envisioned if modernization is allowed to continue unchecked.

The story’s main theme is that humanity should know its limits and not search beyond them because too much knowledge will be our downfall. Thurston’s life is in danger because he has pursued forbidden knowledge. Possessing that knowledge has damaged him psychically to the point where death holds no terror: “I have looked upon all that the universe has to hold of horror, and even the skies of spring and the flowers of summer must ever afterward be poison to me” (287).