Anaximander, who believed that all things arose from the elemental nature of the universe, the "apeiron" (ἄπειρον) or the "unbounded" or "infinite," was likely the first western thinker to propose that life developed spontaneously from nonliving matter. The primal chaos of the "apeiron," eternally in motion, served as a substratum in which elemental opposites (e.g., wet and dry, hot and cold) generated and shaped the many and varied things in the world. According to Hippolytus of Rome in the third century CE, Anaximander claimed that fish or fish-like creatures were first formed in the "wet" when acted on by the heat of the sun and that these aquatic creatures gave rise to human beings. Censorinus, writing in the 3rd century, reports: