意識の成立と構造 --生物体の機能としての観点から

Abstract

Consciousness is a function of an organism; it is a function that has evolved, and by considering it a function of an organism and focusing on the form of consciousness that supposedly is its earliest form, I intend to elucidate a posteriori its essential attributes. In the first section, I criticize B. Libet's thesis, which states that my behaviors are decided by unconscious neural processes before I become aware of the decision. If my behaviors were decided by unconscious processes, both my consciousness and brain regions producing consciousness would be useless. Nature would have eliminated such useless brain regions. But the existence of my consciousness shows that it should increase my behavioral adaptivity. Therefore, free will as a function of consciousness makes behaviors not seemingly but truly more adaptive than unconsciousness does, and hence, it is a crucial function of consciousness. In the second section, I criticize Chalmers' zombie argument. I suppose a kind of "pseudo-zombies, " which, like Chalmers' zombies, have no consciousness but behave as human beings do; however, unlike Chalmers' zombies, my pseudo-zombies do not have the same brain regions that produce consciousness in humans. I show that the evolutional birth of the pseudo-zombie might be far more likely than that of Chalmers' and that the pseudo-zombies are more evolutionarily adaptive than human beings as they are relieved of the burden of their brain regions that produce consciousness. If pseudo-zombies had existed, they would have driven out us. But in fact, it is not they but we that are on earth. Thereby our existence nullifies Chalmers' assumption that zombies without consciousness can act like us. In the last section, I maintain that for free behaviors to increase their adaptiveness, consciousness should not be isolated but be supported by other mental functions such as perception, memory, and synthesizing, which make behaviors appropriate to the circumstance. Therefore, we must study consciousness not by itself but in organisms as a whole. Furthermore, I speculate as to how consciousness was born in brain evolution, which, according to me, might have been born as a kind of bypass of unconscious input-output processes.