Can you outsmart the slippery slope fallacy Elizabeth Cox
On the plains of the Serengeti,
a dung beetle
rolls his perfectly sculpted ball of dung
away from competitors.
In this Canadian river, a beaver
rushes to reinforce her dam
as it threatens to burst.
As the snowball
thunders down the mountainside,
gaining momentum,
the arctic foxes run for cover—
I can’t stand these nature programs.
Always the same story, and not a rational
actor in sight. What else is on?
It’s April 1954, and Vietnamese
nationalists are on the verge of victory
against French forces
fighting for control of Vietnam.
Their victory could lead
to an independent Vietnam
under communist leader Ho Chi Minh.
The United States President,
Dwight D. Eisenhower,
is holding a press conference to comment
on these developments.
Well, if you really must.
Eisenhower claims that by virtue of what
he calls the “falling domino principle,”
communist control of Vietnam would be
the “beginning of a disintegration”
that would be certain
to cause “incalculable loss.”
The beetles and beavers
may be beyond my reach,
but surely here’s someone
I can reason with.
Now, Mr. President,
let’s take a deep breath, shall we?
It’s a big leap—or, one might say,
a long slide—
from communist governance of Vietnam
to the global spread of authoritarian
communist regimes.
It’s as if we were to say
you were clothed,
now you’re in your underwear,
so soon everyone in the world will
be completely naked.
Don’t worry, I may have that power,
but I promise not to use it.
Now, as I was saying,
this kind of argument,
where one step, let’s call it A,
kicks off a string of events
that inevitably culminates
in an extreme scenario,
let’s call it Z,
is known as a slippery slope.
Many such arguments focus on catastrophe,
but the slope to an extreme positive
outcome can be just as slippery.
The trouble with this kind of argument
is that,
in presenting Z
is the inevitable outcome of A,
it almost always overstates the
likelihood that Z will happen
if A happens.
Why?
Allow me to trouble you with some math.
Let’s assume for the sake of argument
that, taken individually,
each step between A and Z is
independent from the others
and very likely—
99%.
So the probability that A causes B,
that B causes C,
that C causes D, and so on,
is each 99%.
Even so, each additional step adds
an opportunity to alter the outcome,
and A is only 78%
likely to lead to Z—
far from an inevitability.
If there’s a 95% likelihood of each step,
the chance that A leads to Z
plummets to about 28%.
If there’s a 90% likelihood
at each step—
still very likely by most standards—
the chance that A leads to Z
is only 7%.
And if 24 of the 25 steps between A and Z
are 99% likely,
and one is 50% likely,
the chance that A leads to Z
goes down from 78% to 39%.
Back to your situation.
I won’t deny you have reason
to be concerned.
You’re warily watching as powerful
authoritarian communist regimes
in the Soviet Union and China try
to spread their form of governance.
But let’s take a look at the chain
of events you suggest:
You say that the countries
surrounding Vietnam
would all soon fall under communist rule;
that this would result in a loss
of essential trade
with these countries for others;
that with no non-communist nations
left to trade with,
Japan would be pressured towards communism
and that this, in turn,
would threaten Australia and New Zealand.
Your ultimate fear, if I may presume,
is that this will in turn threaten
the United States.
Is this a possibility?
Sure.
Where I take issue is
with your comparison to dominos.
These complex real-world events are not,
in fact, like dominoes,
where when the first one falls,
it becomes a certainty that the last
will fall.
For any one of these events, a number
of possible outcomes could result,
each affecting the other events
in different ways.
The possibilities are not a chain,
they’re a web.
It’s 1975, and after 20 years of conflict,
and several million lives lost,
North Vietnamese forces have taken control
of the capital of South Vietnam.
The war is over, and all of Vietnam
is under communist control.
Communist regimes have come to power
in neighboring Laos and Cambodia,
where the regime will be responsible
for the deaths of an estimated quarter
of all Cambodians.
Wait, there’s more.
That first step you were trying
to avoid happened,
but the end result you predicted did not.
As for the steps between, a few happened;
many did not.
Decades afterward,
your fellow humans are still debating
why events unfolded the way they did.
And this is the trouble
with slippery slope arguments.
They focus exclusively
on extreme outcomes,
assigning those outcomes
a degree of certainty or inevitability
that rarely corresponds to reality.
They divert attention from other,
more likely possibilities,
foreclosing discussions that might
be more productive.
And that’s when they’re
made in good faith.
Slippery slope arguments can also be
intentionally structured
to take advantage of people’s fears—
whatever your position on an issue,
it’s easy to come up with an extreme
outcome that suits your aims.
Best to avoid them entirely, eh?