In a very interesting chapter he demonstrates the development of consciousness over the last couple of millennia with reference to mankind’s improving ability to distinguish colors. Initially only black and red were differentiated, but what was perceived as “red” has been refined into red, orange, yellow and white and even further. Likewise with “black” which split up into black and blue-green, from which the separate colors blue and green were again discerned: "The blazing blue of the oriental sky is not mentioned in Homer or the Bible, nor the Rig Veda or Zend Avesta. But in this present century we know not only the seven primitive colors, but literally thousands of different shades and gradations of them."
Bucke argues that new or enhanced senses originate with sporadic manifestations among a minority of human beings and that a new consciousness eventually spreads through the whole population. The new or fourth level of consciousness will enable mankind to perceive the unity of the cosmos and the divine presence inherent in it, liberate humanity from fear and enable the race to perceive that love is the rule and the basis of the universe: this is cosmic consciousness. Bucke predicts that it will ultimately be the norm.