物理論、意志自由與運動控制裡的自我   全文下載

Physicalism, Free Will, and the Self in Motor Control

唯物論與意志自由論之間長久衝突著，現代心靈哲學甚至有論述認為心靈只是物質的副現象，於是危及意志自由存在的觀念。30年前Benjamin Libet提出科學證據，顯示意識意向活動發生之前發生無意識的腦部活動，此研究助長副象論，讓人擔心自由意志並不存在，所謂意志其實只是物質的活動。本文回應這個擔心，討論唯物論的現代版本─物理論，論述心靈解釋不再堅持化約，而要求自然化。本文根據自然化的科學方法論，批評基於化約與實體觀念的心靈解釋，主張心靈具有多層次，當行動者的運動系統在意識層次影響著物理機制對運動指令的選擇，就顯示意志是自由的；再細分，意志自由可見於前反省的三個自我：運動的啟動者、藉由感覺回饋的動作修正者，以及在感覺裡驗收動作的我。運動動作的順暢與精確得自於這些自我之間的合作，這是一個對意志自由的自然化觀點解釋。

A long-standing conflict has been going on between materialism and free will theory. The rise of cognitive science stands with materialism. Philosophy of mind even considers the will to be a mere epiphenomenon. Libet showed that conscious intentional actions are preceded with unconscious processes; as a consequence, the so-called free will is suspected to be a mere illusion. In order to respond to the concern raised, this paper investigates physicalism—the modern version of materialism—and finds that the emphasis on reduction has been replaced with that of naturalization. With a naturalized account, this paper criticizes that the aforementioned conflict stems from the inappropriate application of two notions— substance and reduction—to the notion of the will. Unlike such explanation, this paper argues that the mind involves a variety of levels. When consciousness is shown to be causally efficacious on determining the selection of motor commands, the free will would then be justified. At this point, this paper argues that the motor system receives three ways of determination at the conscious level—that is, identification of the goal that initiates a movement, the modification of movements on grounds of sensory feedbacks, and the approval of successful movements in consciousness. This is a naturalized perspective of free will. It indicates the existence of free will, yet with a different perspective from intuitions.