The sciences, each straining in its own direction, have hitherto harmed us little; but some day the piecing together of dissociated knowledge will open up such terrifying vistas of reality, and of our frightful position therein, that we shall either go mad from the revelation or flee from the deadly light into the peace and safety of a new dark age.
In the first paragraph of Section I, Thurston offers this assessment of the impact of science on humanity and suggests that it will inevitably become a threat. He gains this perspective through the experience of learning about Cthulhu, but because the reader has yet to do the same, his bold statement may initially seem surprising. By beginning with a critique of scientific advancement, Lovecraft sets a precedent for the rest of the story and invites the reader to be suspicious of Thurston’s ongoing quest for knowledge.
Was I tottering on the brink of cosmic horrors beyond man’s power to bear? If so, they must be horrors of the mind alone, for in some way the second of April had put a stop to whatever monstrous menace had begun its siege of mankind’s soul.
This quotation appears in Section III not long after Thurston reads of Johansen’s voyage for the first time in the Sydney Bulletin. Along with the knowledge he gained from the stories of Wilcox and Inspector Legrasse, Johansen’s experience finally enables Thurston to piece together the mystery of the Cthulhu cult and their monstrous leader. He understands the cosmic nature of this discovery, and the first consequence he perceives is a psychological one. The immensity of this information is enough to destroy the mind and “mankind’s soul,” a high price to pay for knowledge.