Man has lost the capacity to foresee and to forestall. He will end by destroying the earth.

In this warning, Schweitzer links modern humanity’s technical power with a moral and imaginative deficit: the failure to anticipate consequences (“foresee”) and to take preventive action (“forestall”). The line fits his broader ethical project—often summarized as “reverence for life”—which insists that progress without ethical restraint becomes self-defeating. Read in an environmental key, the quote anticipates later ecological critiques: when societies treat nature as an inexhaustible instrument and ignore long-term effects, they risk turning their own ingenuity into a mechanism of planetary harm. The stark ending functions as a moral ultimatum: without renewed responsibility, human agency becomes destructive rather than civilizing.