TRUTH, FOR Karl Popper, is not discovered; it is invented. It is, therefore, always a provisional truth, which lasts only as long as it is not refuted. Truth is in the mind, in imagination and reason—not hidden like a treasure in the depths of matter or in the stellar abyss, waiting for the perspicacious explorer to unearth or detect it and to show it to the world like an imperishable goddess. Popper believes that a truth is fragile, continually under the drumfire of tests and experiments that heft it, that try to undermine it (to “falsify” it, according to his vocabulary) or to substitute it for another—a process that has generally happened and will inevitably continue to happen in the course of that vast pilgrimage of humanity through time that we call progress, civilization.