The question suddenly came into my head, 'And if we were all blind?' And then immediately, as if answering myself, 'But we are all blind.'
Um dia, sentado à mesa, pensei: E se fôssemos todos cegos? Imediatamente me veio a resposta: Nós somos todos cegos.
Original text (Portuguese)
Source, in full
On the idea for his next novel (Blindness), which came to him while sitting in a restaurant; New York Times interview with Alan Riding (1998), as quoted in Portuguese Literary & Cultural Studies, 6th Edition (Center for Portuguese Studies and Culture, 2001), p. 131.