Time & Perspective Quote by John Desmond Bernal

Bernal’s sentence has the chill of a scientist refusing to grant comfort. He’s talking about forces that try to dam the mind - censorship, propaganda, institutional pressure, the soft coercion of “acceptable” opinion - and he does it with the cool precision of someone used to measuring outcomes rather than indulging in moral melodrama. The opening clause concedes a present-tense optimism (“pretty clear” they’re ineffective), then immediately punctures it: history doesn’t guarantee progress, and neither does the current mood.

The line works because it’s engineered like a warning label. Bernal doesn’t argue that thought is naturally unstoppable; he treats it as a variable dependent on conditions. “They have not always been so” is the dagger: there were periods when authorities, churches, states, and even scientific orthodoxies successfully narrowed what could be thought, published, or funded. “We cannot be sure” pushes the reader out of complacency. Certainty, in his framing, is a luxury that invites repeat catastrophe.

Context matters: Bernal lived through two world wars, the rise of fascism, and the Cold War’s tightening grip on speech and scientific exchange. A scientist who cared about the social role of science, he understood that ideas don’t float free; they travel through institutions, and institutions can be captured. The subtext is civic, not just philosophical: the freedom to think is a technology that can fail. If you want it to keep working, you maintain it like infrastructure - not with faith, but with vigilance.