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Presentism and Eternalism: Two Philosophical Theories About Time (2)[1]

現時論與永恆論：兩種有關時間的哲學理論(二)

Eternalism contrasts to Presentism and is thought of as its opposite. Eternalism is the philosophical theory which says that all points in time are equally real. The past, the present, and the future are all real. In this sense, Socrates and tomorrow’s events exist right now, even if I cannot see them or interact with them. Many philosophers have adopted Eternalism because they argue that Presentism is contradicted by Einstein’s Special and General Theory of Relativity, whereas Eternalism agrees with it. As the philosopher of science, Dean Rickles puts it: “the consensus among philosophers seems to be that special and general relativity are incompatible with presentism.”

永恆論與現時論的觀點相反。永恆論認為所有的時間點都真的存在。過去、現在和未來都是真的。就這點而言，即使看不到蘇格拉底和明天要做的事，也無法和他們產生任何互動，但是他們卻都共同存在在當下。許多哲學家會接受永恆論是因為他們說現時論與愛因斯坦的狹義和廣義相對論相矛盾，而永恆論則與相對論的看法一致。身為科學哲學家的Dean Rickles說：「哲學家們似乎都認為相對論與現時論兩者的概念有著天壤之別。」

According to the Presentists, there is a flow of time, with the present moment moving forward into the future and leaving the past behind. However, this idea assumes that the present moment will be the same for everyone, an idea which runs up against special relativity. Special relativity says that observers with different frames of reference (such as observers moving at different speeds) can have different perceptions of whether a pair of events happens at the same time or at different times. In addition, someone moving faster than someone else will experience ‘time passing’ slower than they do. The theory also says we have no reason to prefer one observer’s perception to another – both are correct. We, therefore, cannot say that there are a set of events simultaneously happening in the present. People’s ‘present’ is different depending on their frame of reference.

根據現時論者的說法，時間的流逝是從當前的時刻朝著未來前進，而不會朝過去的方向流逝。然而，這個想法卻是建立在「當下」對每個人來說都是一樣的這個假設之下，牴觸了狹義相對論。狹義相對論認為，在不同的參考座標觀察時（例如不同的速度移動），觀察者會對兩件事是同時發生還是不同時發生產生不同的看法。此外，移動速度比較快的人，其時間流逝的速度會比他人更慢。狹義相對論還說，不用覺得只有一個觀察者的看法是對的，因為其實兩人的看法都是正確的。所以，不能說「現在」這些事情都是同時發生的，因為每個人的「現在」都取決於他們各自的參考座標。

In Einsteinian relativity, the ‘present’ is not something which is an absolute element of reality. As Einstein himself said, “People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion”. Eternalism does not necessarily do away with the concepts of past and future, but considers them more like directions – whether something is in the past or future depends entirely on your frame of reference. Eternalism also agrees with general relativity (Einstein’s theory of gravity) in which time becomes a dimension intertwined with the three dimensions of space. This is known as four-dimensional space-time. Time, therefore, becomes part of the physical structure of the universe and things in the past or future will eternally exist, so long as the structure of the universe eternally exists. Since distinctions between the past, present and future are illusory, we can think of all objects and events as being timeless or eternal.

在愛因斯坦的相對論中，「現在」並非現實的絕對要素。就像愛因斯坦所說的，「像我們這樣相信物理的人都知道，過去、現在和未來的區別只是一種一廂情願的錯覺。」永恆論並不是說要排除掉過去和未來的概念，而是將它們視為方向，無論是過去還是未來，都完全取決於你的參考座標。永恆論也認同廣義相對論（愛因斯坦的重力理論），在廣義相對論中，時間成了一個與其他三個維度空間相互交織在一起的維度，這就是所謂的四維時空。時間成為宇宙物理結構的一環，只要宇宙的結構永遠存在，過去或未來的事物也將永遠存在。既然過去、現在和未來的區別只是錯覺，那麼，我們就可以將所有的人事物都當作不會受到時間影響或是永恆的存在。

Even though it seems like common sense that there is a ‘flow of time’, this could just be a subjective illusion. The sense of this flow of time is extremely convincing, but it probably just reflects how our brains have evolved. If we did not make distinctions between the past, present and the future, perhaps this would hinder our ability to survive. In fact, looking to the past for lessons and planning for the future seems to be essential components of any survival strategy. Our brains are simply not equipped to perceive the true nature of time. Eternalism has also been described as the “Block Universe” theory since all of the points in space-time are fixed and unchanging. Everything, in a sense, exists now. This theory does, however, have some controversial implications for free will. For example, if the future is fixed, then in what sense can I really make a conscious choice to do something?

雖然「時間的流逝」看似稀鬆平常，但是，這可能只是一種主觀上的錯覺。即便這種時間流逝的感覺相當真實，但這可能只是反映出大腦的進化。如果沒有去區分過去、現在和未來的話，可能會限制了我們的生存能力。事實上，記取過去的教訓以及規劃未來的方向似乎都是生存策略中相當重要的一環。而我們的大腦根本就無法察覺到時間的本質。因為所有的時間點都是固定不變的，所以，永恆論又被稱為「塊狀宇宙」理論。從某種意義上來說，所有的事物都存在在「此刻」。不過，永恆論的內涵卻也引發了一些與自由意志相關的爭議。例如，假如說未來已經固定不會變了，那麼，怎麼樣才能真正做出有意識的選擇呢？