1.61803 writes:
Spiritual existance is important for man to believe in because man bases much of his religious beliefs in such. To deny the existance of ghost and spirits is to deny the possibility of life after death. And man so much wants to believe that his existance and his soul will trancend his human mortality.
Because to think otherwise is uncomfortable. To think that one simply ceases to exist post death is far to bleak. Much better to believe in the metaphysical.
By the same token, it may be that spiritual existence is important for some men to deny because, due to their wickedness, the possibility of receiving recompense for their sins is too bleak.