Darwin's idea works like a universal acid that dissolves inherited certainties

Dennett opens with a memorable image from his own childhood imagination: a liquid so corrosive it eats through any container meant to hold it, including glass and steel. He argues Darwin's theory of natural selection functions the same way intellectually, eating through nearly every traditional concept it touches, from the idea of a divine creator to assumptions about the unique, non-mechanical status of human minds, and leaving behind a transformed but still recognizable worldview.

Crucially, Dennett insists this corrosiveness isn't a reason to fear or resist the idea, but a sign of its explanatory power. Unlike an actual dangerous substance, Darwin's idea is, in his view, simply true, and the appropriate response to a true but unsettling idea is to accept its implications fully rather than trying to contain it artificially within safe boundaries, such as pretending it applies only to simple organisms and not to human cognition or ethics.

Takeaway: an idea that dissolves your assumptions isn't dangerous because it's false, it's dangerous because it's true.