Lecture 12-7 - Why Walter Should Shave His Head

From "Think Again: How to Reason and Argue" on Coursera

Okay. (I'm not arguing. I'm simply
explaining why I'm right)

Finally, as the last argument in this
course, as the one that bothers me most,

and it comes from Lauren Brush.

I think it must have bothered her too,
because it's not clear

that she was ever happy with the
formulation and kept changing it.

But I'm going to give a very simplified
version of it, and

see if we can reconstruct it and determine
whether it's really sound.

This is what Lauren said --
in my words, not hers, exactly.

"Walter wants to up the number of students
who get the most out of this class."

Now that's true.

I want to increase the number of students
who get the most out of this class.

That's the point of teaching.

"Therefore, Walter should shave his hair on
camera

and, make the video open to all students."
No!

My beautiful locks, no!

That is what's upsetting.
But luckily, luckily

[LAUGH]

this argument's not valid, now way.
It's possible for the premises to be true

and the conclusion false:
so, sorry Lauren, I'm not convinced.

Uh-oh, she can add another premise.
She's probably assuming this.

More students will get the most
out of this class

if Walter shaves his hair on camera and
makes the video open to all students.

Okay, okay,
I guess I gotta admit that too.

I think people will get more outta the
class if they see that,

because part of what you get outta this
class is you have some fun.

At least I hope you've had fun, I have.

Okay Lauren.
But still, still it's not valid.

It's not valid, and so I'm not going to
shave my head yet, no way, no way.

Uh-oh,

the main reason it wasn't valid was that the
premises were about what I want,

and the conclusion is about what I should do.

But wait, now maybe it is valid.

It sure looks valid if we add one more suppressed
premise.

Walter should do what will accomplish
what he wants to do.

Oh my gosh, if what I want to accomplish

is to get more students
to get the most out of the class,

if I should do what I want to do,
then I should --

do what's going to make the most students
get the most out of the class.

And if shaving my head is doing that,

then it sure looks like

I should shave my head on camera

and make it open to all the students.

I feel like I'm in trouble now.

What's going to happen?

Oh, wait! Wait!
I've got it!

Even though it's valid,
premise 3 is not true:

that I should do
what's going to accomplish what I want?

What if I want something like,
I want to smoke?

Well, maybe I shouldn't go to the store
and get a pack of cigarettes,

because even though I want to smoke,
I still shouldn't,

because it's bad for me,
because it's going to hurt me.

So, it looks like you have to qualify
that premise by saying that I should do

what will accomplish what I want to do,
unless doing it has worse effects,

like in smoking,
when it might give me cancer and hurt me.

So whew, now I'm safe.

Now I don't have to shave my head, ah!

Ah! Oh! that makes me feel better
because you can't get the conclusion

that I should do it
from those three premises, right?

It's not valid anymore.

Uh-oh, uh-oh, all we need is another
premise.

Walter shaving his hair, his head, on
camera

and making the video open to all students
will not have worse effects.

Tss -- uh-oh.

because shaving my head is not going to
give me cancer, like smoking.

Matter of fact, hair will grow back.

It's not -- it might be embarrassing
for a few days but only a few days.

That's not that bad compared to all those
students out there in Courseraland.

And, so I guess I have to admit that
premise four is true.

But wait a minute, if the argument is
valid and premise four is true,

and premise three is true
and premise two is true,

premise one is true.

Now it's looking good.

And we can even break it up to make it
easier to understand.

I want the number of students to increase

that get the most out of the course

and more will get most out of the course

if I shave my head on camera
and make that video available.

So, shaving my hair on camera and making the
video available would give me what I want

and I ought to do want I want if it
doesn't cause worse harm.

This is not going to cause worse harm,
so I ought to do it.

Oh my gosh.

Now I'm worried because

that means that the conclusion is true.

If the argument is sound, it's valid,

and the premises are true,
then the conclusion is sound.

Or at least if I accept the premises
and the conclusion follows validly,

then I'm committed to that conclusion.

I'm committed to the fact that
I should shave my hair on camera

and distribute the video to all students,
so you can all watch it.

Lauren has convinced me of that.

But, notice this argument applies to me,
it also applies to Ram.

So if I've gotta shave my head,
Ram's got to shave his beard.

So, although I have to shave my head,
at least I'm not alone.

Guess we gotta both go do it.