1
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Oh the humanity!

2
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Ah... humanity...

3
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It’s a trainwreck,
but I can’t look away.

4
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It’s 1843, and a debate is raging 
among physicians

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about one of the most common 
killers of women: childbed fever.

6
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Childbed fever strikes 
within days of giving birth,

7
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killing more than 70% of those infected—
and nobody knows what causes it.

8
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Obstetrician Charles Meigs has a theory.

9
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Having observed abdominal inflammation

10
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in patients who go on 
to develop the fever,

11
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he claims this inflammation 
is the cause of childbed fever.

12
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Much of the medical establishment
supports his theory.

13
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Oh, come on!

14
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They really leave me no choice 
but to teach them some skepticism.

15
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That’s better.

16
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Now, Meigs, your argument is based 
on a fallacy— the false cause fallacy.

17
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Correlation does not imply causation:

18
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When two phenomena regularly occur
together,

19
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one does not necessarily 
cause the other.

20
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So you say women who have inflammation
also come down with childbed fever,

21
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therefore the inflammation 
caused the fever.

22
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But that’s not necessarily true.

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Yes, yes, the inflammation comes first,
then the fever,

24
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so it seems like the inflammation 
causes the fever.

25
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But by that logic, since babies 
usually grow hair before teeth,

26
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hair growth must cause tooth growth.

27
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And we all know that’s not true,
right?

28
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Actually, don’t answer that.

29
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A couple of different things 
could be going on here.

30
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First, it’s possible that fever 
and inflammation are correlated

31
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purely by coincidence.

32
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Or, there could be a causal relationship
that’s the opposite of what you think—

33
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the fever causes the inflammation,

34
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rather than the inflammation 
causing the fever.

35
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Or both could share a common 
underlying cause you haven’t thought of.

36
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If I may, just what do you think 
causes inflammation? Nothing?

37
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It just is? Really?

38
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Humor me for a moment in discussing
one of your colleague’s ideas—

39
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Dr. Oliver Wendell Holmes.

40
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I know, I know, 
you don’t like his theory—

41
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you already wrote 
a scathing letter about it.

42
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But let’s fill your students in, shall we?

43
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Holmes noticed a pattern: 
when a patient dies of childbed fever,

44
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a doctor performs an autopsy.

45
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If the doctor then treats a new patient,

46
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that patient often comes 
down with the fever.

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Based on this correlation

48
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between autopsies of fever victims
and new fever patients,

49
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he proposes a possible cause.

50
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Since there’s no evidence that the autopsy
causes the fever beyond this correlation,

51
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he doesn’t jump to the conclusion 
that autopsy causes fever.

52
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Instead, he suggests that doctors 
are infecting their patients

53
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via an invisible contaminant 
on their hands and surgical instruments.

54
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This idea outrages most doctors, 
who see themselves as infallible.

55
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Like Meigs here, who refuses 
to consider the possibility

56
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that he’s playing a role 
in his patients’ plight.

57
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His flawed argument doesn’t leave any 
path forward for further investigation—

58
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but Holmes’ does.

59
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It’s 1847, and physician Ignaz Semmelweis

60
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has reduced the number 
of childbed fever deaths

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in a clinic from 12% to 1% 
by requiring all medical personnel

62
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to disinfect their hands after autopsies
and between patient examinations.

63
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With this initiative, he has proven
the contagious nature of childbed fever.

64
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Ha!

65
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It’s 1879, and Louis Pasteur 
has identified

66
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the contaminant responsible 
for many cases of childbed fever:

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Hemolytic streptococcus bacteria.

68
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Hmm, my fries are cold.

69
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Must be because my ice cream melted.