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>> We've looked at a couple of examples of
deductive arguments.

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We've seen one example of a sound
deductive argument.

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That proves a conclusion that's
interesting, a conclusion that we wouldn't

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of heretofore have expected.
We've also looked at an example of a

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deductive fallacy.
Now, I'd like to consider a deductive

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argument that's also fallacious, but the
fallacy in the deductive argument can be

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spotted if we remember our Week five
lessons about categorical logic.

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The deductive argument I have in mind is,
All Babies Are Evil.

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By Cameron Smith.
Here's how Cameron's argument goes.

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Premise one.
Humans should not cause discomfort to

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other people.
Premise two.

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Causing discomfort to other people is
selfish and cruel.

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Premise three.
Ignorance is no excuse for being selfish

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and cruel.
Premise four, humans that are selfish and

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cruel are evil.
Premise five, all people who live with a

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baby are caused to have sleep deprivation
by that baby making noise.

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Premise six, making noise as other people
try to sleep, causes discomfort.

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Premise seven.
All those who live with a baby complain of

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the mess caused by that baby.
Premise eight.

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Babies never clear up any of the mess that
they make.

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Premise nine.
Humans who do not clear up any of the mess

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that they make cause discomfort to other
people.

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Premise ten.
Babies are human.

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And so, the conclusion of those ten
premises is babies are evil.

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Now, at first glance, that argument might
appear valid and the ten premises of the

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argument might appear true and so, the
argument appears to be sound, it appears

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to be a valid argument.
With entirely true premises.

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But I don't think the conclusion is true.
So I think either the argument is not

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valid, or one or more of the premises is
not true.

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But which one?
Well, I think we can see which one.

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If we specify which quantifier is being
used in the premises that make a general

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statement about humans, are we using the
quantifier all or are we using the

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quantifier most?
If the statements about humans are

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understood as statments that use the
quantifier all, then we can use Venn

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diagrams to show that this argument is
actually valid.

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This argument is valid if the quantifier
that's being used in all the premises

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about humans is the quantifier all.
But, if the quantifier that's being used

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in the premises about humans is the
quantifier most, then Venn diagrams don't

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demonstrate the validity of this argument.
And in fact the argument is not valid.

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So whether the argument is valid or not
depends on precisely which quantifier is

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being used in those premises about humans.
Is that the quantifier all or the

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quantifier most?
If it's the quantifier all, then the

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argument is valid.
Unfortunately, the premises are not all

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true, and they're not all true because
it's not entirely true that all humans Who

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cause discomfort or pain, are evil.
But, if the argument uses the quantifier

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most, then while the premises are true,
the argument isn't valid.

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And Venn diagrams don't help us to show
that it's valid.

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Because Venn diagrams don't represent the
quantifier most, as we saw in Week five.

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So either the argument is valid, but not
all of its premises are true, or the

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argument has entirely true premises, bu
it's not valid.

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Either way the argument is not sound and
so it does not succeed in proving that all

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babies are evil.
Despite the enormous plausibility of the

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argument.