Supporting an inference with logical reasoning and evidence | Reading | Khan Academy

- [Instructor] Hello readers.

Let's play detective, shall we?

My mama always told me not
to jump to conclusions,

but that's essentially what
the skill of inference is.

It's not really a guess.

It's combining what you already know

with what's in front of you

and drawing conclusions from there.

It's filling in the gaps.

So look, I can look at
this shape with gaps in it,

and based on what the shape suggest

and based on what I already know,

I can say I'm pretty
sure that's an elephant.

When I do that, I'm making an inference.

That's what we're gonna
talk about in this video.

Not just making an inference,

but going back and supporting

that inference with evidence.

This is an essential skill.

Knowing how to read between the lines

can help you make sense of
what's missing in a text,

of what's being left unsaid,

or maybe even to figure
out if someone is lying.

Let me set up an example, a
little locked room mystery.

There was a mouse hole
in the wall of a kitchen.

There is a heavy glass jar
full of lovingly baked cookies

with a heavy glass lid still on the jar.

An hour ago, there were
a dozen cookies in there,

and now there are only six.

From the jar across the floor

to the mouse hole in the wall,

there is a trail of cookie crumbs.

The question readers is, therefore,

who took the cookies?

The answer is not a mouse.

A mouse did not take the cookies.

It's a things to set up.

It's a frame job.

How do I know that?

The lid.

Based on my background
knowledge about mice,

I don't think a mouse
would've been able to lift

and replace the heavy
glass lid of the jar.

Maybe if we knew a person
had left the lid off the jar,

the mouse would still be a suspect.

But I can infer from the evidence I see

and my background knowledge

that someone else took six cookies

and left it incriminating
cookie crumb trail

that led to the doorstep
of an innocent mouse.

And when I am defending
this mouse in court,

I will point to the lid as evidence

in support of my inference.

Let's do this again.

But I'll give you a chunk of text

to look at and then you'll get the chance

to make your own inferences.

Here is the first introduction

of Agatha Christie's fictional
detective Hercule Poirot.

The narrator describes Poirot.

Poirot was an extraordinary
looking little man.

He was hardly more than
five feet, four inches,

but carried himself with a great dignity.

His head was exactly the shape of an egg,

and he always perched
it a little on one side.

His mustache was very stiff and military.

The neatness of his attire
was almost incredible.

I believe the speck of
dust would've caused him

more pain than a bullet wound.

Yet, as a detective, his
flare had been extraordinary,

and he had achieved
triumphs by unraveling some

of the most baffling cases of the day.

And for you, I have a
question now, readers.

Based on this description,

what personality traits
do you think Poirot

has that make him good
at solving mysteries?

I'll put on some music,

or you can take this time to
pause the video and discuss.

We'll meet back here and I'll show you

how to answer this question

by making some informed inferences.

(upbeat music)

Okay, let's go through it.

So what traits does
Poirot have that make him

good at solving mysteries?

I think the words I'd
use to describe Poirot

are fussy or detail-oriented.

How do I know that?

Let's go to the text.

He carries himself with great dignity.

He's proud of his appearance.

He has this stiff little mustache.

"The neatness of his attire

was almost incredible."

That is to say, literally
incredible, unbelievable.

His clothes were so neat, unbelievably so

to the point where a speck of dust

would hurt him like a bullet hurt someone.

All those details lead me to conclude

that he notices little things.

You have to notice the little things

if you're going to keep yourself so neat.

So exquisitely tidy and free of dust,

a spectacular attention to detail.

I can infer that that's
the personality trait

that leads him to notice things

other people wouldn't notice,

and makes him such a great detective.

As you read, it's
important to keep checking

for text evidence that supports

or discredits your initial inferences.

Sometimes they'll be
wrong, sometimes right.

But usually the rest of the text

will help you determine that.

Now, do I suspect that
you or I or any of us

are likely to become
mystery solving sleuths?

Well, yes, actually I do.

I just think it'll be through the skill

of inference in your reading practice

and not through solving murders.

Though from the evidence presented,

I wouldn't rule out that possibility.

You can learn anything, David, out.