Modus
Ponens versus
Likely the most commonly witnessed failure of logic
when debating the intransigent political fanatic or the fundamentalist religious
extremist is known as affirming the consequent. Unless put
into perspective this fallacy is a bit difficult to comprehend, but once
defined the logical failure becomes evident.
Affirming the consequent is categorical in nature
and essentially relies on reversing the argument to make available evidence fit
or confirm a bias. A recent example is the contorted ballyhoo that followed the
Department of Defense announcement that vintage chemical weapons had been
unearthed in Iraq. The right wing machine went into full tilt boogie
proclaiming that the Bush/Cheney justifications for invading that country had
been vindicated. This in spite of the DoD stating in the very same report that
the shells were completely useless and had been for decades.
The premise in such an argument is actually valid,
yet there is a glaring error between the premise and conclusion. The motive of
the right-wingers is to foment the false assumption that the premise (Saddam
had WMDs) is actually the conclusion. In truth, the premise is only one of
several conditions required to prove the conclusion. Let’s look at it from a
child’s eyes so that even the most biased, bigoted extremist might be able to
understand.
To state that ducks are birds and that ducks swim in the
water is the primary premise. The secondary premise would be to state that
chickens are birds. The false conclusion would come by stating that since both
ducks and chickens are birds, and ducks swim in the water, that chickens also
swim in the water. Of course we know this to be incorrect because experience
tells us that swimming is neither necessary nor a sufficient condition to
define a bird.
We call this “getting the cart before the horse”,
and it seems to be the ultimate in confirmation bias… a last port in the storm
for the bigoted.
Let’s take this to politics.
Obama nationalized health care by passing the
Affordable Care Act. The Nazis had nationalized health care. Therefore Obama is
just like Hitler. It is difficult to understand how so many Americans cannot
understand that nationalized health care is insufficient evidence to define Nazism.
This is especially true since every country that fought against the Nazis now
has nationalized health care, with the exception of the U.S.
Now let’s consider religion, specifically
creationism.
Because of the backlash by rational, scientific
thinkers, the fundamentalists prefer to call it Intelligent Design. In what has
become known as the watchmaker analogy, the creationist tries to prove that
just as a watch could not accidentally come to exist, so neither could a human
being. Every creationist argument will find roots in the watchmaker argument.
Probably the best known of these arguments comes
from Michael Behe, who calls it “Irreducible Complexity.” In his book, Darwin’s
Black Box, Behe posits that certain systems are so complex that they cannot
be explained by the accidental nature of evolution. He uses a mousetrap as his
example. Ken Ham is fond of using a banana. Bill O'Reilly rather bizarrely uses
the tides.
The premise is that a mousetrap (banana, the tides)
was created… that it is the product of intelligent design… that it is an irreducibly
complex object composed of several parts, all of which contribute to the
function. The universe, and particularly humans, are also composed of several
parts and almost unimaginably complex… therefore an intelligent designer must
be involved.
By now you have figured out how to decipher
attempts to affirm the consequent, so I suspect you can finish the story.
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