or the safety of vaccines

每天我們要面對各種各樣的問題，

where we have to answer questions whose answers

例如氣候變遷、疫苗安全等，

rely heavily on scientific information.

我們必須回答這些問題，

Scientists tell us that the world is warming.

而答案很大程度上依賴於科學資訊，

Scientists tell us that vaccines are safe.

科學家告訴我們世界正在暖化，

But how do we know if they are right?

科學家告訴我們疫苗是安全，

Why should be believe the science?

但我們怎麼知道他們是對的？

The fact is, many of us actually don't believe the science.

為什麼我們要相信科學？

Public opinion polls consistently show

事實上，很多人並不相信科學。

that significant proportions of the American people

民意調查一直顯示，

don't believe the climate is warming due to human activities,

大部分美國民眾

don't think that there is evolution by natural selection,

並不相信氣候暖化是 人為活動造成的，

and aren't persuaded by the safety of vaccines.

也不認為有物競天擇這回事，

So why should we believe the science?

也不相信疫苗的安全。

Well, scientists don't like talking about science as a matter of belief.

那麼，為何我們應該相信科學？

In fact, they would contrast science with faith,

科學家不喜歡把科學 說成是需要「相信」的事。

and they would say belief is the domain of faith.

說實話，他們認為 「科學」和「信仰」是相斥的，

And faith is a separate thing apart and distinct from science.

他們說「教義」只屬於 「信仰」的一部份，

Indeed they would say religion is based on faith

而「信仰」和「科學」 兩者本是風馬牛不相及。

or maybe the calculus of Pascal's wager.

他們甚至說宗教以信仰為基礎，

Blaise Pascal was a 17th-century mathematician

或者像帕斯卡的賭注：

who tried to bring scientific reasoning to the question of

布萊茲．帕斯卡是 17 世紀的數學家，

whether or not he should believe in God,

他要把科學辯證帶入討論

and his wager went like this:

應否相信上帝的存在。

Well, if God doesn't exist

他打的賭是這樣：

but I decide to believe in him

嗯，如果上帝不存在，

nothing much is really lost.

但我決定相信上帝的存在，

Maybe a few hours on Sunday.

那我真的沒太大損失，

(Laughter)

（可能損失了禮拜天的幾小時。）

But if he does exist and I don't believe in him,

（笑聲）

then I'm in deep trouble.

然而，如果上帝真的存在， 而我沒有相信上帝，

And so Pascal said, we'd better believe in God.

那我就大遭殃啦。

Or as one of my college professors said,

所以帕斯卡說， 我們最好還是相信上帝吧。

"He clutched for the handrail of faith."

或者，如同我其中一個 的大學教授說：

He made that leap of faith

「他抓著信念不放，

leaving science and rationalism behind.

視為天降神跡，

Now the fact is though, for most of us,

把科學或理性思考遺忘掉。」

most scientific claims are a leap of faith.

現在事實卻是，

We can't really judge scientific claims for ourselves in most cases.

對很多人來說，很多科學主張 也沒有實驗基礎。

And indeed this is actually true for most scientists as well

我們也很難判斷某些科學主張，

outside of their own specialties.

甚至很多科學家也未能判斷

So if you think about it, a geologist can't tell you

超出其專長領域的主張。

whether a vaccine is safe.

所以你想一想， 地質學家就無法告訴你

Most chemists are not experts in evolutionary theory.

疫苗到底是否安全。

A physicist cannot tell you,

大多數化學家也不是 演化理論的專家。

despite the claims of some of them,

一個物理學家也無法跟你說，

whether or not tobacco causes cancer.

儘管某些人有自己的主見，

So, if even scientists themselves

吸煙到底會否致癌。

have to make a leap of faith

所以，即使科學家

outside their own fields,

在超出自己的專長領域外，

then why do they accept the claims of other scientists?

都只相信天降神跡，

Why do they believe each other's claims?

那樣他們為什麼接受 其他科學家所提出的科學主張呢？

And should we believe those claims?

那樣他們為什麼 接受其他人的主張呢？

So what I'd like to argue is yes, we should,

那樣我們應該相信他們的主張嗎？

but not for the reason that most of us think.

所以我認為，是的， 我們應該相信，

Most of us were taught in school that the reason we should

但不是大部分人想的原因。

believe in science is because of the scientific method.

大部分人在學校接受教育，

We were taught that scientists follow a method

我們應該相信科學， 原因是其科學方法。

and that this method guarantees

老師說科學家遵循一套方法，

the truth of their claims.

而這套方法

The method that most of us were taught in school,

確保理論正確。

we can call it the textbook method,

大部份人在學校裡 學習的那套方法，

is the hypothetical deductive method.

我們稱之為課本上的方法，

According to the standard model, the textbook model,

就是「假說演繹法」。

scientists develop hypotheses, they deduce

根據標準的模式， 教科書教材的模式，

the consequences of those hypotheses,

科學家們提出假說，

and then they go out into the world and they say,

推論那些假說的結果，

"Okay, well are those consequences true?"

然後他們到現實世界去驗證，

Can we observe them taking place in the natural world?

「好，結果是否如我所料？」

And if they are true, then the scientists say,

我們可否在自然界中 觀察到這樣的結果嗎？

"Great, we know the hypothesis is correct."

如果可以，科學家就會說，

So there are many famous examples in the history

「太棒了，我們知道假說是正確的。」

of science of scientists doing exactly this.

科學史上有很多著名的例子，

One of the most famous examples

科學家就是這樣做的。

comes from the work of Albert Einstein.

其中一個有名的例子

When Einstein developed the theory of general relativity,

來自愛因斯坦的理論。

one of the consequences of his theory

當愛因斯坦提出廣義相對論時，

was that space-time wasn't just an empty void

他的其中一個論點是，

but that it actually had a fabric.

空間和時間不是空洞，沒有實體的，

And that that fabric was bent

事實上其結構為纖維交織似的，

in the presence of massive objects like the sun.

而且在質量很大的物體面前， 例如太陽，

So if this theory were true then it meant that light

時空就會被扭曲。

as it passed the sun

那麼假設這個論點是正確的，

should actually be bent around it.

意味着當光線穿越太陽時，

That was a pretty startling prediction

就會圍繞著太陽而扭曲。

and it took a few years before scientists

那是一個很驚人的預測，

were able to test it

而科學家要到好多年後，

but they did test it in 1919,

才能夠去檢驗理論。

and lo and behold it turned out to be true.

他們在1919年進行測試，

Starlight actually does bend as it travels around the sun.

真怪呀，結果證明是真的：

This was a huge confirmation of the theory.

星光行經太陽時， 確實發生彎曲。

It was considered proof of the truth

這對相對論是很重大的確證，

of this radical new idea,

它被認為對這個全新想法　

and it was written up in many newspapers

提供真實證明，

around the globe.

全球各大報社也爭相報導。

Now, sometimes this theory or this model

全球各大報社也爭相報導。

is referred to as the deductive-nomological model,

現在，這個理論或模式

mainly because academics like to make things complicated.

有時候被稱作「演繹－律則」模式，

But also because in the ideal case, it's about laws.

主要的原因是 學術界喜歡把事情搞得很複雜，

So nomological means having to do with laws.

而且在理想情況下， 這跟「定律」有關。

And in the ideal case, the hypothesis isn't just an idea:

「律則」就必定跟「定律」有關。

ideally, it is a law of nature.

在理想的情況下， 假說不僅是一種想法：

Why does it matter that it is a law of nature?

這是自然界的定律。

Because if it is a law, it can't be broken.

自然界定律為什麼重要？

If it's a law then it will always be true

因為定律不能被打破。

in all times and all places

如果它是定律，就永遠都是正確的，

no matter what the circumstances are.

無論何時何地，

And all of you know of at least one example of a famous law:

在任何情況下都是正確的。

Einstein's famous equation, E=MC2,

你們所有人都知道 至少一個著名定律的例子：

which tells us what the relationship is

愛因斯坦的著名方程式： E 等於 MC 平方。

between energy and mass.

告訴我們能量與質量的關係，

And that relationship is true no matter what.

告訴我們能量與質量的關係，

Now, it turns out, though, that there are several problems with this model.

而那個關係無論如何都是正確的。

The main problem is that it's wrong.

但是，我們後來發現 一些有關這個模式的問題，

It's just not true. (Laughter)

主要的問題是，它是錯的。

And I'm going to talk about three reasons why it's wrong.

這並不是正確的。（笑聲）

So the first reason is a logical reason.

我要舉出三個原因， 說明它為何是錯。

It's the problem of the fallacy of affirming the consequent.

第一個是邏輯上的原因，

So that's another fancy, academic way of saying

這是有關肯定後件謬誤的問題， (affirming the consequent)

that false theories can make true predictions.

那是另一個異想天開的、 學術上的說法，

So just because the prediction comes true

就是錯誤的理論 也可得到正確的預測結果，

doesn't actually logically prove that the theory is correct.

所以即使預測正確，

And I have a good example of that too, again from the history of science.

邏輯上也未能證明 理論是正確的。

This is a picture of the Ptolemaic universe

我可以再舉一個 科學史上很好的例子，

with the Earth at the center of the universe

這是一張托勒密宇宙的圖片，

and the sun and the planets going around it.

地球處於宇宙的中心，

The Ptolemaic model was believed

而太陽及其他行星圍繞著地球運轉。

by many very smart people for many centuries.

很多聰明人都相信 托勒密宇宙模型，

Well, why?

已有幾個世紀了。

Well the answer is because it made lots of predictions that came true.

嗯，為什麼呢？

The Ptolemaic system enabled astronomers

答案是，因為很多預測結果 的確符合現實狀況。

to make accurate predictions of the motions of the planet,

天文學家根據托勒密系統，

in fact more accurate predictions at first

精確預測行星運動，

than the Copernican theory which we now would say is true.

事實上較哥白尼的理論 都要精準很多，

So that's one problem with the textbook model.

但是我們現在都知道 哥白尼的理論才正確。

A second problem is a practical problem,

這就是教科書教材模式的問題。

and it's the problem of auxiliary hypotheses.

第二個問題是實務問題，

Auxiliary hypotheses are assumptions

跟輔助性假說有關。

that scientists are making

輔助性假說是科學家提出假設，

that they may or may not even be aware that they're making.

有時候他們甚至不會發現 自己提出了假設，

So an important example of this

一個重要的例子就來自

comes from the Copernican model,

哥白尼的模型，

which ultimately replaced the Ptolemaic system.

而最終它取代托勒密系統，

So when Nicolaus Copernicus said,

當尼古拉．哥白尼說，

actually the Earth is not the center of the universe,

地球實際上不是宇宙的中心，

the sun is the center of the solar system,

太陽才是太陽系的中心，

the Earth moves around the sun.

地球是繞著太陽運轉。

Scientists said, well okay, Nicolaus, if that's true

科學家們說：好啊，尼古拉， 如果你說的是真的，

we ought to be able to detect the motion

那我們應該感覺得到 地球在移動，

of the Earth around the sun.

繞著太陽跑。

And so this slide here illustrates a concept

這張投影片展示出

known as stellar parallax.

恆星視差的概念。

And astronomers said, if the Earth is moving

天文學家說：如果地球正在移動，

and we look at a prominent star, let's say, Sirius --

那麼我們觀察一顆明亮的星星時， 譬如說天狼星，

well I know I'm in Manhattan so you guys can't see the stars,

嗯，我知道在曼哈頓， 你們是看不到星星的，

but imagine you're out in the country, imagine you chose that rural life —

但想像一下，你們到鄉村， 選擇過著農村生活，

and we look at a star in December, we see that star

我們在十二月的時候看星，

against the backdrop of distant stars.

就看到遙遠恆星的背景 襯托着天狼星，

If we now make the same observation six months later

如果我們六個月後 再做同樣的觀測，

when the Earth has moved to this position in June,

在6月時，當地球已轉到這個位置，

we look at that same star and we see it against a different backdrop.

我們在不同的背景下， 看著同一顆星，

That difference, that angular difference, is the stellar parallax.

那種差異，那種角度的差異，　　　 就是恆星視差（斗轉星移）。

So this is a prediction that the Copernican model makes.

所以這是根據哥白尼理論 所作的預測，

Astronomers looked for the stellar parallax

天文學家觀測尋找恆星視差，

and they found nothing, nothing at all.

但就沒有觀測到，沒有發現。

And many people argued that this proved that the Copernican model was false.

因此很多人認為 這證明哥白尼的模型是錯的。

So what happened?

所以這是怎麼回事？

Well, in hindsight we can say that astronomers were making

嗯，事後看來，我們可以說，

two auxiliary hypotheses, both of which

天文學家作出兩個輔助性假說，

we would now say were incorrect.

我們現在都知道兩者並不正確。

The first was an assumption about the size of the Earth's orbit.

第一個是有關「地球運行軌道」 大小的假設。

Astronomers were assuming that the Earth's orbit was large

天文學家假設地球的軌道

relative to the distance to the stars.

遠大於跟恆星的距離。

Today we would draw the picture more like this,

今天我們畫出來的圖 比較像這樣：

this comes from NASA,

這幅來自美國太空總署，

and you see the Earth's orbit is actually quite small.

你們可以看到地球的軌道 事實上相當地小，

In fact, it's actually much smaller even than shown here.

其實較這張圖畫還要小，

The stellar parallax therefore,

因此，恆星視差非常小，

is very small and actually very hard to detect.

很難偵測到的。

And that leads to the second reason

這也帶到第二個原因，

why the prediction didn't work,

為什麼沒有觀測到，

because scientists were also assuming

因為科學家也誤以為

that the telescopes they had were sensitive enough

當時的望遠鏡夠精密，

to detect the parallax.

足以偵測到視差。

And that turned out not to be true.

而最後發現這是錯的。

It wasn't until the 19th century

直到19世紀，

that scientists were able to detect

科學家才有辦法偵測到恆星視差。

the stellar parallax.

科學家才有辦法偵測到恆星視差。

So, there's a third problem as well.

所以，還有第三個問題。

The third problem is simply a factual problem,

第三個問題簡而言之 就是事實問題。

that a lot of science doesn't fit the textbook model.

有很多科學不符合教科書上的方法論，

A lot of science isn't deductive at all,

很多科學根本不是 推理演繹出來的，

it's actually inductive.

而是歸納出來的。

And by that we mean that scientists don't necessarily

意思是說，科學家不一定要

start with theories and hypotheses,

先建立理論假設，

often they just start with observations

他們常常只是從觀察出發，

of stuff going on in the world.

觀察世上萬物的運行。

And the most famous example of that is one of the most

最有名的例子查爾斯．達爾文， 也是世上最有名的科學家之一，

famous scientists who ever lived, Charles Darwin.

最有名的例子查爾斯．達爾文， 也是世上最有名的科學家之一，

When Darwin went out as a young man on the voyage of the Beagle,

達爾文年輕的時候 參與小獵犬號的航行，

he didn't have a hypothesis, he didn't have a theory.

他沒有假設，沒有理論，

He just knew that he wanted to have a career as a scientist

只知道要成為一位科學家，

and he started to collect data.

他開始蒐集資料。

Mainly he knew that he hated medicine

主要是他知道他不喜歡醫學，

because the sight of blood made him sick so

看到血會感到不舒服，

he had to have an alternative career path.

因此不得不選擇另一條路。

So he started collecting data.

所以他開始收集資料。

And he collected many things, including his famous finches.

他收集很多東西， 包括他最出名的雀鳥，

When he collected these finches, he threw them in a bag

他把收集的雀鳥丟到包裡，

and he had no idea what they meant.

他也不知道這有什麼意義。

Many years later back in London,

多年以後他回到倫敦，

Darwin looked at his data again and began

達爾文再把資料拿出來看，

to develop an explanation,

然後開始建立學說，

and that explanation was the theory of natural selection.

就是說明物競天擇的理論。

Besides inductive science,

除了歸納法，

scientists also often participate in modeling.

科學家們也常建立模型。

One of the things scientists want to do in life

科學家一生中的志業之一，

is to explain the causes of things.

就是解釋事物的緣由。

And how do we do that?

我們要怎麼做呢？

Well, one way you can do it is to build a model

嗯，一種方法是建立一個模型，

that tests an idea.

然後做測試，

So this is a picture of Henry Cadell,

這是一張亨利．卡道爾的照片，

who was a Scottish geologist in the 19th century.

他是 19 世紀的蘇格蘭地理學家。

You can tell he's Scottish because he's wearing

可以看出他是蘇格蘭人，

a deerstalker cap and Wellington boots.

因為他頭戴獵鹿帽，腳穿威靈頓長靴。

(Laughter)

〔觀眾笑〕

And Cadell wanted to answer the question,

卡道爾想要找出答案，

how are mountains formed?

山巒是如何形成的？

And one of the things he had observed

其中他觀察到一件事，

is that if you look at mountains like the Appalachians,

若看看像是 「阿帕拉契」這座山脈，

you often find that the rocks in them

你們常常會看到裡面的岩石

are folded,

有很多褶皺，

and they're folded in a particular way,

而且是一種特定的摺法，

which suggested to him

讓他覺得

that they were actually being compressed from the side.

它們像是從一邊被擠壓 而形成的褶皺。

And this idea would later play a major role