"There is no man so blind as one who has made up his mind"

Blindness here is not a failure of eyesight but of attention and openness. Once certainty hardens, the mind stops scanning for nuance and contrary evidence, like a lighthouse switched off because the map looks familiar. The decision becomes a filter: information that confirms it slides through; what challenges it is deflected as noise or threat. Curiosity withers, questions are retired, and learning is replaced by defense. Such blindness can feel like strength, decisiveness, clarity, resolve, yet it often masks a quiet fear of being unsettled by reality.

The pattern shows up everywhere. In politics, ideology can turn into armor so thick that facts merely clang against it. In medicine, a clinician who anchors on an early diagnosis may ignore subtle signs that point elsewhere. In investment, conviction can morph into sunk-cost loyalty, blinding one to shifting fundamentals. In relationships, a fixed story about a person, saint or villain, prevents seeing their complexity and development. Technology amplifies the problem: algorithms feed us what we already agree with, and the comfort of echo chambers becomes a surrogate for wisdom. The more total the commitment to a conclusion, the more invisible the world outside its borders becomes.

None of this condemns conviction itself. Commitments are necessary to act, to build, to persevere. The danger lies in mistaking a working hypothesis for a final verdict. Sight is recovered by practicing intellectual humility: holding views firmly but revisably, seeking disconfirming evidence, and asking, What would change my mind? It requires listening as an act of inquiry rather than combat, and noticing the tug of identity that makes some ideas feel nonnegotiable. Paradoxically, the clearest vision belongs to those willing to revise their map. To see, one must let the world update the mind; to remain blind, one need only keep it closed.