To explain this logically, consider Lovecraft's storytelling as a syllogism:
Premise 1: The universe contains ancient, powerful entities and truths that predate humanity and operate on scales beyond our perception (e.g., the Great Old Ones like Azathoth or Yog-Sothoth).
Premise 2: Knowledge of these entities—arcane lore—is preserved in hidden forms (books, ruins, dreams) but is inherently corrupting because it exposes the illusion of human centrality and control.
Conclusion: Encountering the arcane disrupts rational sanity, as the human mind, evolved for earthly survival, cannot reconcile with cosmic indifference. This leads to themes of inevitable doom, where seeking the arcane is akin to opening Pandora's box.
This framework is consistent across Lovecraft's works and those of his contemporaries (the "Lovecraft Circle"), who expanded the mythos with shared elements like additional grimoires or entities. Unlike traditional fantasy where arcane magic might empower heroes, in Lovecraft, it dehumanizes and destroys, reflecting his materialist philosophy influenced by early 20th-century science and his personal atheism.
In summary, "arcane" in Lovecraft's worlds logically embodies the perilous intersection of secrecy, the occult, and cosmic horror—knowledge that is hidden for good reason, yet irresistibly draws the curious to their ruin. This concept has influenced modern horror, from films like The Void to games like Call of Cthulhu, where the arcane remains a symbol of forbidden insight.