So, we're going to start to record.

Can you see the slides now?

Can somebody answer by voice?

No, we don't see presentation slides now.

Good, that's what I wanted to know.

Now you should see the slides.

Excellent, then we're ready to go.

So, last time we were looking at language, talking about phenomena, and I was trying to shorten your eyes and hearing and thinking about what the problems of language might be.

And then,

that's kind of the empirical side of what we're doing.

The more important side for us here is the modeling side.

How can we deal with all of these funny phenomena?

And I would like to kind of talk about what modeling might actually be.

The philosophy of science is called epistemology.

That brings a couple of words with it that I would like to define and talk to you about.

We've started out with this. We started talking about propositions being statements about the world.

Think of them as English sentences.

If you have propositions, propositions are things we can believe.

I can believe that the sun is shining outside.

Those propositions being statements can be true or false.

Or unknown. Very often unknown.

And then, I can still, an agent, still believe in these things.

And if we chose to call knowledge to be justified true belief.

To know something, it has to be true.

You cannot know wrong things. You can believe wrong things until you're blue in the face.

But just them turning out to be true is not enough.

I believe that in computer science, I think, P is not equal to NP.

I do not know it yet because I don't have any justification other than, oh, if she's writing my Tommy or something, that's not really justification.

So that's knowledge.

And knowledge is really what it's all about.

And the question is, how can we make knowledge?

And there is a method for that, often called the scientific method.

And so we, the scientific method is by observing something.

And we've already done that.

We've observed the sentence, the king of Buganda is rich.

And we've observed things about it.

That's what we're observing.

Our universe of discourse.

And what certain statements do, right?

This sentence, the Buganda sentence is true or it's true if there is bloody blood.

That's kind of thing.

So observation, very importantly, needs an observer.

And all of this language data is something we want to have observed,

ideally by a native speaker of English.

If we don't have those around, we'll just say you and me, if people were not native, but maybe good enough.

Okay. So observations may be unreliable.

That's why we want to take native speakers.

But the importance, if the observations are unreliable, you want to observe observations that are reproducible.

Where when you have the same proposition, you kind of reliably and reproducibly can observe the same thing.

That's what physics does, right?