Darwin trained for the ministry before his five-year voyage on HMS Beagle, and returned with the observations that would eventually become On the Origin of Species (1859). The theory of evolution by natural selection reframed natural suffering in ways no theodicy had anticipated: competition, predation, extinction, and parasitism are not aberrations in an otherwise good order but the mechanisms by which the order works. In his private letters to the American botanist Asa Gray, Darwin wrestled candidly with what his own theory implied about the goodness of any creator who designed such a system. His faith eroded gradually over his lifetime, not through philosophical argument but through the accumulating evidence of what nature actually does.