Name: 哲学。条件式Pt.1 (Philosophy: Conditionals Pt. 1)
Uploaded: 2021-01-14T05:43:29.000Z
Duration: 4 min 52 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

and I am an assistant professor[br]of philosophy at MIT.

Today we are going to[br]look at conditionals,

that have puzzled philosophers[br]for thousands of years.

Here's an example of a[br]conditional sentence from a speech

by former presidential[br]candidate, Mitt Romney:

"If the safety net needs[br]repair, I will fix it."

Conditional sentences, like[br](1), consist of two parts:

an antecedent ("the[br]safety net needs repair")

"What do conditional[br]sentences, like (1), mean?"

In other words, by uttering this sentence,

Here's a way to think about[br]questions of meaning like this.

What has Mitt Romney[br]told us by uttering it?

One way of figuring out[br]what Romney has told us

is to get clear on what[br]he has not told us.

He hasn't told us that the[br]safety net needs repair,

and he also hasn't told us that[br]he will fix the safety net.

Rather, what he said is that[br]there is some connection

between the safety net needing[br]repair and his fixing it.

Romney has told us that it is not the case

that the safety net needs[br]repair and he won't fix it.

either the safety net doesn't need repair,

Let's call this theory the[br]"material conditional theory."

Philo of Megara have been[br]attracted to this theory

In order to state the[br]material conditional theory

more precisely, we will[br]make use of a device

depends on the truth values of its parts,

in this case, the antecedent[br]and consequent of (1).

Let's start with a simple[br]example of a conjunction.

"The cat is on the mat,[br]and the cat is fat."

Naturally, someone who says[br]this tells you two things:

that the cat is on the mat,[br]and that the cat is fat.

if both the cat is on the[br]mat and the cat is fat,

and false if either the[br]cat isn't on the mat

We draw this dependence of the truth value

noting "T" for true when[br]the sentence is true,

and "F" for false when[br]the sentence is false.

the first two columns contain[br]every possible combination

of assigning either "T" or[br]"F" to the parts of (3).

in the row where both[br]of its parts have "T"s.

This captures the fact[br]that conjunctions are true

only if both of their conjuncts are true,

since that is the only condition[br]under which it is true.

Okay, so now what about our[br]conditional sentence (1)?

According to the material[br]conditional theory,

that the safety net needs[br]repair and Romney won't fix it.

where it is true that the[br]safety net needs repair

This assignment of[br]truth values, therefore,

entirely captures the meaning[br]of the conditional (1)

according to the material[br]conditional theory.

Now, although the material[br]conditional theory

You might have noticed that,[br]according to the theory,

In the next video, we will[br]explore some challenges