Do We Have Free Will? 我們有自由意志嗎？

🔊The clearest statement of the worry was written in 1814 by the French mathematician Pierre-Simon Laplace. “We ought then to regard the present state of the universe as the effect of its anterior state and as the cause of the one which is to follow.” Imagine an intelligence that knew, at one instant, all the forces of nature and the position of every particle, and that was vast enough to calculate with them. “For it, nothing would be uncertain and the future, as the past, would be present to its eyes.” This is determinism: given the state of the world at one time and the laws of nature, only one future is possible. Laplace’s intelligence, which later writers called his demon, would know what you will have for breakfast on a morning ten years from now.

把這個憂慮說得最清楚的，是法國數學家拉普拉斯在 1814 年寫下的一段話。「因此，我們應當把宇宙的現在狀態，看作它先前狀態的結果，以及隨後狀態的原因。」設想有一個智能，在某一瞬間知道自然界所有的力，以及每一個粒子的位置，並且龐大到足以拿這些資料來計算。「對它來說，沒有什麼是不確定的；未來就像過去一樣，會呈現在它眼前。」這就是決定論：給定世界在某一時刻的狀態，加上自然定律，就只有一個未來是可能的。拉普拉斯的這個智能，後人稱之為他的「惡魔」，會知道十年後的某個早上你要吃什麼早餐。

🔊A century and a half earlier, Baruch Spinoza had drawn the conclusion without flinching. “Nothing in the universe is contingent,” he wrote. Everything that happens follows from the nature of things with the same necessity by which the angles of a triangle add up to two right angles. People believe otherwise for a reason he states exactly: “men are mistaken in thinking themselves free; their opinion is made up of consciousness of their own actions, and ignorance of the causes by which they are conditioned.” We notice our desires and do not notice where they come from. “Thus an infant believes that of its own free will it desires milk, an angry child believes that it freely desires vengeance, a timid child believes that it freely desires to run away.” In a letter he imagined a stone that became conscious while flying through the air. It would suppose, he said, that it was moving because it wished to.

比這早一個半世紀，史賓諾莎就毫不退縮地得出了這個結論。他寫道：「宇宙中沒有任何東西是偶然的。」發生的一切，都從事物的本性必然地推出，就像三角形的內角和等於兩個直角那樣必然。人們之所以不這麼相信，他把理由說得很精確：「人們自以為自由，這是錯的；他們這個意見的由來，是意識到自己的行動，卻不知道決定這些行動的原因。」我們察覺到自己的欲望，卻沒有察覺它們從哪裡來。「於是嬰兒相信，他是憑自己的自由意志想喝奶；生氣的孩子相信，他是自由地想要報復；膽小的孩子相信，他是自由地想要逃跑。」在一封信裡，他設想有一顆石頭在空中飛的時候有了意識。他說，那顆石頭會以為，自己是因為想動才動的。

🔊Suppose determinism is true. Then, the argument runs, nobody could ever have done anything other than what he did. The thief could not have refrained and the hero could not have run away. It seems unfair to blame a person for what he could not help, and pointless to praise him. Philosophers who accept this reasoning are called hard determinists. They conclude that moral responsibility, in the sense of deserving reward or punishment, is an illusion, and that we should treat wrongdoers as we treat the sick or the dangerous, with treatment and restraint and without resentment. Spinoza recommended exactly that attitude: not to laugh at human actions, or weep at them, or hate them, but to understand them.

假設決定論是真的。那麼，這個論證說，從來沒有人能做出他實際所做之外的任何事。小偷不可能忍住不偷，英雄不可能逃跑。為了一個人不由自主的事而責備他，似乎不公平；稱讚他，似乎也沒有意義。接受這個推理的哲學家，稱為硬決定論者。他們的結論是：道德責任，就「理應受賞或受罰」這個意思而言，是一個幻覺；我們對待做錯事的人，應該像對待病人或危險的人那樣，給予治療與約束，而不帶怨恨。史賓諾莎建議的正是這種態度：對人的行為，不嘲笑，不哀嘆，不憎恨，而是去理解。

🔊One reply accepts that determinism and freedom cannot both be true, and concludes that determinism is false. Those who take this line are called libertarians, in a sense that has nothing to do with politics. They hold that when I choose, I start a new chain of causes that was not fixed by anything earlier. The ancient atomist Epicurus thought that atoms occasionally swerve for no reason, and some modern writers appeal to the indeterminacy of quantum physics. The standing objection is that chance is no better than necessity. If my arm moves because of a random event in a neuron, the movement is a twitch, and a twitch is not a choice.

一種回應承認決定論與自由不可能同時為真，然後推斷：決定論是假的。採取這條路線的人稱為自由意志論者（libertarian，這個詞在這裡跟政治無關）。他們主張，當我做選擇的時候，我開啟了一條新的因果鏈，它不是由先前的任何東西決定的。古代的原子論者伊比鳩魯認為，原子偶爾會毫無理由地偏斜；有些現代作者則訴諸量子物理的不確定性。對這條路線的一貫反駁是：機遇並不比必然好。如果我的手臂是因為神經元裡的一個隨機事件而動，那個動作只是抽搐，而抽搐不是選擇。

🔊The other reply is that the conflict was never real. This is compatibilism, and its classic statement is Hume’s: “By liberty, then, we can only mean a power of acting or not acting, according to the determinations of the will; that is, if we choose to remain at rest, we may; if we choose to move, we also may.” Freedom, on this view, is the absence of constraint. A prisoner in chains is unfree. So is a person at gunpoint, or in the grip of a compulsion he would give anything to be rid of. A person who does what he wants, for his own reasons, is free, and it makes no difference that his wants have causes. Indeed they had better have causes, since an action that sprang from nothing in my character would hardly be mine. The contemporary philosopher Harry Frankfurt refined the idea. What matters is whether the desire I act on is one that I want to have, as the addict’s craving is not.

另一種回應是：衝突從來就不是真的。這是相容論，它的經典陳述出自休謨：「那麼，所謂自由，我們只能是指一種依照意志的決定而行動或不行動的能力；也就是說，如果我們選擇保持靜止，我們可以；如果我們選擇移動，我們也可以。」照這個看法，自由就是沒有強制。戴著鎖鍊的囚犯是不自由的。被槍指著的人也是，被某種他願意付出一切代價擺脫的強迫性衝動攫住的人也是。一個人做他想做的事、出於他自己的理由，就是自由的；至於他的欲望有原因，這毫無差別。事實上，它們最好有原因：一個不是從我的性格中任何東西產生的行動，很難說是我的行動。當代哲學家法蘭克福把這個想法磨得更細：要緊的是，我據以行動的那個欲望，是不是一個我「想要擁有」的欲望；而成癮者的渴求並不是。

🔊Chinese philosophers argued about ming (命), which means both “fate” and “what is decreed.” The Mohists attacked fatalism as a doctrine that ruins people. If the rich are fated to be rich and the poor to be poor, then, as the fatalists say, effort is useless, and a ruler who believes it will stop governing and a farmer will stop plowing. Mozi called this teaching a great harm to the world. Mencius drew a finer line. Some things, he said, are such that “if you seek them you get them, and if you neglect them you lose them,” because the seeking is within yourself. Others depend on what is outside, and there, seeking is no help to getting. Virtue is of the first kind and wealth and long life are of the second. This is not a theory of causation. It is closer to the compatibilist’s point, that the question of what is in my power can be answered by looking at what responds to my effort, without first settling the metaphysics.

中國哲學家爭論的是「命」，這個字既指「命運」，也指「被決定的」。墨家攻擊宿命論，說它是一種毀人的學說。如果富人命中注定富、窮人命中注定窮，那麼正如主張有命的人所說，努力是沒有用的；相信這一套的君主會不再治理，農夫會不再耕田。墨子稱這種說法是「天下之大害」。孟子畫了一條更細的線。他說，有些東西是「求則得之，舍則失之」的，因為「求在我者也」。另一些取決於外在，在那裡，「求無益於得也」。德行屬於第一類，富貴與長壽屬於第二類。這不是一套因果理論。它比較接近相容論者的論點：要回答「什麼在我的能力之內」，可以看什麼東西會回應我的努力，而不必先把形上學解決。

🔊In 1983 the physiologist Benjamin Libet asked volunteers to flex a wrist whenever they felt like it and to note the moment at which they became aware of the urge. Electrodes on the scalp showed a build-up of activity in the brain about half a second before the movement, and about a third of a second before the reported decision. Many people took this as proof that the conscious will arrives too late to cause anything. The interpretation is disputed. The actions were trivial and unreasoned, the timing of an inner event is hard to report, and later work suggests that the early signal may reflect background fluctuation and not a decision already made. A compatibilist adds that the result would not matter in any case. A decision made by my brain is a decision made by me.

1983 年，生理學家利貝特請受試者想動的時候就彎一下手腕，並且記下自己察覺到那股衝動的時刻。頭皮上的電極顯示，在動作之前大約半秒，腦中就出現了活動的累積；這比受試者回報的「決定」時刻，早了大約三分之一秒。許多人把這當作證據，證明有意識的意志來得太晚，不可能是任何事的原因。這種解讀有爭議。那些動作是瑣碎而不涉及理由的；內在事件的時間點很難回報；後來的研究也顯示，早期的訊號反映的可能是背景波動，而不是一個已經做出的決定。相容論者還會補一句：無論如何，這個結果都無關緊要。由我的大腦做出的決定，就是由我做出的決定。

🔊Suppose you became convinced that there is no free will. What would you do differently? You would still have to decide what to eat. You could not sit back and wait to see what you were determined to do, since sitting back would be one of the options. P. F. Strawson argued in 1962 that our practices of gratitude, resentment, and forgiveness do not rest on a theory that might be refuted. They are part of what it is to live with other people, and no argument could lead us to give them up wholesale. What can change is their tone. A person who sees how much of anyone’s character was shaped by things he did not choose may judge others more gently and take less credit for himself. On that modest conclusion Spinoza, Hume, Mencius, and the Buddha are closer together than their theories would lead one to expect.

假設你被說服了，相信沒有自由意志。你會有什麼不同的做法？你還是得決定吃什麼。你沒辦法往後一靠，等著看自己「被決定」去做什麼，因為往後一靠也是選項之一。史陶生在 1962 年論證：我們感激、怨恨與寬恕的種種做法，並不是建立在一個可能被駁倒的理論上。它們是「跟別人一起生活」這件事的一部分，沒有哪個論證能讓我們把它們全盤放棄。能改變的是它們的調子。一個人如果看清，任何人的性格有多少是由他沒有選擇的東西塑造的，他對別人的判斷也許會溫和一些，對自己的功勞也會少居一些。在這個平實的結論上，史賓諾莎、休謨、孟子與佛陀彼此的距離，比他們的理論讓人預期的要近。