 While casting ghosts and spirits in metaphysical terms that in certain respects seemed intent on explaining away ghosts and spirits, Neo-Confucians also affirmed that just as yin and yang pervade reality, so do ghosts and spirits. The spirits are simply the expansive and ghosts, the contractive forces of the world. Recognizing the interrelatedness of ghosts and spirits with the world at large, many Neo-Confucians associated spirits with heaven, spring and summer, morning, the sun, light, music, and so on, while ghosts were linked to the earth, fall and winter, evening, the moon, darkness, rituals, and so forth. With this analysis, Neo-Confucians did not deny spirits, but instead asserted that they infuse every aspect of reality just as surely as do yin and yang.