By declaring that I think, therefore I am, Descartes recognised a key element of human brain action, its remarkable capacity for self-awareness, a subtle component of human consciousness that received little attention until recently. Zoltan Torey (2009) argues that it accompanied the evolution of that other key superiority of human brain action, language. Because language is a motor function, he deduces that evolution developed its proprioceptive feedback into self-awareness. Of course the mental capacity for self-awareness needs considerable conscious effort to realise its potential. Without effort it need not advance beyond the brutish animal level.
Cynics hold that the masses manage to exist without thought. The effectiveness of demagogues and charlatans seems proof enough. Hitler, expressed it most bluntly. In Mein Kampf he held that the masses are blind and stupid. He proved it. Imposing those words on the German mass as a compulsory school text did not dissuade them from following him. He captured them with commonly held prejudice. Humans do not recognise the subservience of individual minds to the beliefs of the mass, the group mind, which provides the essential tools of human thought. I call the slavery meme tyranny (see Epilogue in Bell, 2015).