How can we get a valid argument form from talk of morality?
我们怎样从道德的谈论中得到一个有效的论点形式呢？
Do you see how that argument is valid?
你看到这个论点怎样有效了吗？
You, you give me the definition of a valid argument.
你们给我一个有效论点的定义。
Q Here is a valid argument form. If P then Q. P therefore Q.
这里有一个有效的论点形式，如果P，那么Q，P所以。
Okay does everyone see why this is a valid argument?
大家都明白为什么这是有效论点了吧？
This argument is valid and has false premises?
这个论点是有效的，前提为假？
So again we have a deductively valid argument but it's not deductively valid in actually we're a lot further on in modal logical then we are in deontic logic.
所以我们有一个演绎的有效论点,但是这不是演绎有效的,实际上我们模态逻辑有很多要讲的,然后我们再讲道义逻辑。
What you gave me wasn't a valid argument do you have another one?
你给我的不是一个有效的论点，你们还有吗？
Actually a valid argument doesn't have true premises and true conclusion what is a valid argument?
实际上一个有效论点没有真前提和真结论，什么是有效论点呢？
Once you have got an valid argument you can add anything you like and it will still be valid.
一旦你有一个有效论点，你可以加任何东西，他依然有效。
So if we see the conclusion of a valid argument is false what do you know? A little bit longer.
如果我们看到有效论点的结论为假，你们知道什么？有一点长。
So what do we know? This is a valid argument isn't it? Yes?
我们知道什么呢？这是个有效论点，不是吗？
Do you think an argument could be valid if all its premises of the argument is false?
你们认为一个论点，如果前提为假，可能有效吗？
Do you see how that is-if that's a deductively valid argument it in the virtue of the meaning of the word wrong. Isn't it?
你们明白，如果那是一个演绎有效的论点，它是通过错误这个词的意思，不是吗？
If we can show the conclusion of a valid argument - put your hand up-if we can show the conclusion of a valid argument is false what do we know?
如果我们可以展示有效论点的结论-，举手，如果我们可以展示，有效论点的结论为假，我们知道什么？
So if you negate that conclusion and took away the therefore, if you negated that conclusion the set would be inconsistent wouldn't it? And that shows you that that's a valid argument.
如果你否认结论，把所以拿掉，那么，如果你否认结论，这就不一致了，不是吗？这显示这是一个有效论点。
This is a deductively valid argument and its truth preserving and therefore it is very, very useful.
这是个演绎的有效论点，保留了真理，所以非常有用。
Now that looks like a deductively valid argument doesn't it?
这看起来像演绎有效的论点，不是吗？
And that's what tells you whether the argument is valid or not So this is a deductively valid argument and this is a fallacy.
这是他告诉你结论是否有效，这是演绎有效的论点，这是一个谬论。
This argument is valid and this argument is invalid.
这个论点有效，这个论点无效。
So the fallacy of fast talking, and the list of fallacies are down there just for you amusement Okay here's a fallacy, well deductively valid argument and here's a fallacy that looks like it.
快速谈话的谬论，谬论的清单是供你们娱乐的，这里有个谬论，演绎的有效论点，有谬论看起来像。
Could the argument be valid if the premises are false?
前提为假，论点可能有效吗？
这个论点有效吗？
It's only sound if it's a valid argument and it has true premises.
如果是有效论点才会完好，他有真前提。
So it's a valid argument but has false premises. Okay what about if it is an invalid argument with false premises.
这是个有效的论点但是有假前提，如果是无效论点有假前提呢？
And I am saying actually the discovery that the valid argument is that the conclusion in which is false can be hugely important.
我说实际上发现那是有效论点，结论为假，可能很重要。
That's right. So if you have a valid argument a deductively valid argument in which the conclusion is false then you know one of the premises must be false.
对，所以如果论点有效，一个演绎的有效论点中结论是假的，你就知道前提中有一项是假的。
And as soon as you understand that and as soon as you stop thinking of a valid argument having true premises and true conclusion you will see what's going on here.
只要你们明白,只要停止思考有效论点有,真前提和真结论，你们就明白了。
Could this argument be valid say yes - as a matter of fact this argument must be valid.
这个论点有效，说对-，实际上这个论点肯定有效。
So you could have a valid argument in which the premises are all false.
一个有效论点可能,前提都为假。
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