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Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:00.07,0:00:03.91,Default,,0000,0000,0000,,[Music]
Dialogue: 0,0:00:03.91,0:00:07.45,Default,,0000,0000,0000,,Scientists often gather data through
Dialogue: 0,0:00:07.45,0:00:10.96,Default,,0000,0000,0000,,observation experiments, archival studies
Dialogue: 0,0:00:10.96,0:00:14.31,Default,,0000,0000,0000,,and so on. But they are rarely satisfied
Dialogue: 0,0:00:14.31,0:00:17.53,Default,,0000,0000,0000,,with data alone. Scientists want to draw
Dialogue: 0,0:00:17.53,0:00:20.06,Default,,0000,0000,0000,,conclusions from those data. They want to
Dialogue: 0,0:00:20.06,0:00:21.97,Default,,0000,0000,0000,,use the data to show that certain
Dialogue: 0,0:00:21.97,0:00:24.59,Default,,0000,0000,0000,,theories are right and others are wrong.
Dialogue: 0,0:00:24.59,0:00:27.86,Default,,0000,0000,0000,,To understand science, then, it will be
Dialogue: 0,0:00:27.86,0:00:29.68,Default,,0000,0000,0000,,important to understand when it is
Dialogue: 0,0:00:29.68,0:00:31.85,Default,,0000,0000,0000,,legitimate and when it is illegitimate.
Dialogue: 0,0:00:31.85,0:00:35.32,Default,,0000,0000,0000,,To draw a specific conclusion from what
Dialogue: 0,0:00:35.32,0:00:40.04,Default,,0000,0000,0000,,we already know we need to understand
Dialogue: 0,0:00:38.07,0:00:42.57,Default,,0000,0000,0000,,the difference between good and bad
Dialogue: 0,0:00:40.04,0:00:45.21,Default,,0000,0000,0000,,arguments; and that is why, in this
Dialogue: 0,0:00:42.57,0:00:49.47,Default,,0000,0000,0000,,lecture, we will take a look at logic--the
Dialogue: 0,0:00:45.21,0:00:53.34,Default,,0000,0000,0000,,study of argumentation. Let us first
Dialogue: 0,0:00:49.47,0:00:56.16,Default,,0000,0000,0000,,introduce some terminology. An argument
Dialogue: 0,0:00:53.34,0:00:59.40,Default,,0000,0000,0000,,consists of two parts: the premises and
Dialogue: 0,0:00:56.16,0:01:02.22,Default,,0000,0000,0000,,the conclusion. The premises are the
Dialogue: 0,0:00:59.40,0:01:06.29,Default,,0000,0000,0000,,things we presuppose and the conclusion
Dialogue: 0,0:01:02.22,0:01:08.48,Default,,0000,0000,0000,,is what we conclude from those premises.
Dialogue: 0,0:01:06.29,0:01:12.24,Default,,0000,0000,0000,,So let's look at an example:
Dialogue: 0,0:01:08.48,0:01:15.99,Default,,0000,0000,0000,,No medieval King had absolute power over
Dialogue: 0,0:01:12.24,0:01:20.67,Default,,0000,0000,0000,,his subjects. Louis 7 of France was a
Dialogue: 0,0:01:15.99,0:01:23.07,Default,,0000,0000,0000,,medieval King. So Louis 7 of France did
Dialogue: 0,0:01:20.67,0:01:26.55,Default,,0000,0000,0000,,not have absolute power over his
Dialogue: 0,0:01:23.07,0:01:29.58,Default,,0000,0000,0000,,subjects. Here the first two lines are
Dialogue: 0,0:01:26.55,0:01:33.36,Default,,0000,0000,0000,,the premises and a final line introduced
Dialogue: 0,0:01:29.58,0:01:35.67,Default,,0000,0000,0000,,by the word "so" is the conclusion. In this
Dialogue: 0,0:01:33.36,0:01:38.16,Default,,0000,0000,0000,,argument we assume that medieval kings
Dialogue: 0,0:01:35.67,0:01:40.74,Default,,0000,0000,0000,,did not have absolute power and that
Dialogue: 0,0:01:38.16,0:01:43.20,Default,,0000,0000,0000,,Louis 7 was a medieval King. And we
Dialogue: 0,0:01:40.74,0:01:47.33,Default,,0000,0000,0000,,conclude that he did not have absolute
Dialogue: 0,0:01:43.20,0:01:50.07,Default,,0000,0000,0000,,power. As a second piece of terminology
Dialogue: 0,0:01:47.33,0:01:53.55,Default,,0000,0000,0000,,we will make a distinction between valid
Dialogue: 0,0:01:50.07,0:01:55.61,Default,,0000,0000,0000,,and invalid arguments. A valid argument
Dialogue: 0,0:01:53.55,0:01:58.47,Default,,0000,0000,0000,,is an argument in which the conclusion
Dialogue: 0,0:01:55.61,0:02:01.68,Default,,0000,0000,0000,,really follows from the premises.
Dialogue: 0,0:01:58.47,0:02:04.32,Default,,0000,0000,0000,,Our example about Louis 7 is an example
Dialogue: 0,0:02:01.68,0:02:07.38,Default,,0000,0000,0000,,of a valid argument. The conclusion
Dialogue: 0,0:02:04.32,0:02:10.41,Default,,0000,0000,0000,,really follows from the premises. It
Dialogue: 0,0:02:07.38,0:02:12.78,Default,,0000,0000,0000,,makes sense to draw this conclusion from
Dialogue: 0,0:02:10.41,0:02:15.93,Default,,0000,0000,0000,,these premises.
Dialogue: 0,0:02:12.78,0:02:19.02,Default,,0000,0000,0000,,As an example of an invalid argument we
Dialogue: 0,0:02:15.93,0:02:22.14,Default,,0000,0000,0000,,can take this: No medieval King had
Dialogue: 0,0:02:19.02,0:02:25.08,Default,,0000,0000,0000,,absolute power over his subjects. Louis
Dialogue: 0,0:02:22.14,0:02:27.63,Default,,0000,0000,0000,,seven of France was a great horseman. So
Dialogue: 0,0:02:25.08,0:02:31.95,Default,,0000,0000,0000,,Louis seven of France did not have
Dialogue: 0,0:02:27.63,0:02:34.53,Default,,0000,0000,0000,,absolute power over his subjects. We just
Dialogue: 0,0:02:31.95,0:02:37.55,Default,,0000,0000,0000,,can't draw that conclusion from those
Dialogue: 0,0:02:34.53,0:02:41.22,Default,,0000,0000,0000,,premises. So this argument is not valid.
Dialogue: 0,0:02:37.55,0:02:42.48,Default,,0000,0000,0000,,It's invalid. Note that whether an
Dialogue: 0,0:02:41.22,0:02:44.10,Default,,0000,0000,0000,,argument is valid or not
Dialogue: 0,0:02:42.48,0:02:46.70,Default,,0000,0000,0000,,has nothing to do with whether the
Dialogue: 0,0:02:44.10,0:02:49.71,Default,,0000,0000,0000,,premises or the conclusions are true.
Dialogue: 0,0:02:46.70,0:02:52.20,Default,,0000,0000,0000,,Perhaps Louis 7 really was a great
Dialogue: 0,0:02:49.71,0:02:54.42,Default,,0000,0000,0000,,horseman. Then all the premises and the
Dialogue: 0,0:02:52.20,0:02:58.02,Default,,0000,0000,0000,,conclusion of that argument are true and
Dialogue: 0,0:02:54.42,0:03:01.17,Default,,0000,0000,0000,,yet the argument is invalid because the
Dialogue: 0,0:02:58.02,0:03:04.35,Default,,0000,0000,0000,,conclusion just doesn't follow from the
Dialogue: 0,0:03:01.17,0:03:06.84,Default,,0000,0000,0000,,premises. On the other hand it's also
Dialogue: 0,0:03:04.35,0:03:10.62,Default,,0000,0000,0000,,possible to have false premises and a
Dialogue: 0,0:03:06.84,0:03:12.18,Default,,0000,0000,0000,,valid argument. For instance: No medieval
Dialogue: 0,0:03:10.62,0:03:14.76,Default,,0000,0000,0000,,King had absolute power over his
Dialogue: 0,0:03:12.18,0:03:17.85,Default,,0000,0000,0000,,subjects. Victor Gijsbers was a
Dialogue: 0,0:03:14.76,0:03:20.36,Default,,0000,0000,0000,,medieval king. So Victor Gijsbers did not
Dialogue: 0,0:03:17.85,0:03:24.18,Default,,0000,0000,0000,,have absolute power over his subjects.
Dialogue: 0,0:03:20.36,0:03:25.59,Default,,0000,0000,0000,,This argument is perfectly valid even
Dialogue: 0,0:03:24.18,0:03:30.14,Default,,0000,0000,0000,,though the assumption that I am a
Dialogue: 0,0:03:25.59,0:03:33.00,Default,,0000,0000,0000,,medieval King is, as far as I know, false.
Dialogue: 0,0:03:30.14,0:03:35.61,Default,,0000,0000,0000,,We can now introduce our final piece of
Dialogue: 0,0:03:33.00,0:03:38.82,Default,,0000,0000,0000,,terminology: The distinction between two
Dialogue: 0,0:03:35.61,0:03:42.27,Default,,0000,0000,0000,,kinds of arguments. Deductive arguments
Dialogue: 0,0:03:38.82,0:03:44.34,Default,,0000,0000,0000,,and inductive arguments. A deductive
Dialogue: 0,0:03:42.27,0:03:46.31,Default,,0000,0000,0000,,argument is an argument in which the
Dialogue: 0,0:03:44.34,0:03:49.35,Default,,0000,0000,0000,,truth of the premises
Dialogue: 0,0:03:46.31,0:03:52.50,Default,,0000,0000,0000,,absolutely guarantee the truth of the
Dialogue: 0,0:03:49.35,0:03:54.48,Default,,0000,0000,0000,,conclusion. It's just not possible for
Dialogue: 0,0:03:52.50,0:03:56.87,Default,,0000,0000,0000,,the premises to be true and the
Dialogue: 0,0:03:54.48,0:03:59.43,Default,,0000,0000,0000,,conclusion to be false.
Dialogue: 0,0:03:56.87,0:04:01.80,Default,,0000,0000,0000,,Teturning to our original example, we can
Dialogue: 0,0:03:59.43,0:04:03.15,Default,,0000,0000,0000,,see that this is a deductive argument. It
Dialogue: 0,0:04:01.80,0:04:04.95,Default,,0000,0000,0000,,is true
Dialogue: 0,0:04:03.15,0:04:07.53,Default,,0000,0000,0000,,the medieval Kings did not have absolute
Dialogue: 0,0:04:04.95,0:04:10.62,Default,,0000,0000,0000,,power; and if it is true that Louis 7 was
Dialogue: 0,0:04:07.53,0:04:13.20,Default,,0000,0000,0000,,a medieval King, then it must be true
Dialogue: 0,0:04:10.62,0:04:15.60,Default,,0000,0000,0000,,that he did not have absolute power.
Dialogue: 0,0:04:13.20,0:04:18.03,Default,,0000,0000,0000,,Or, in other words, if he did have
Dialogue: 0,0:04:15.60,0:04:22.68,Default,,0000,0000,0000,,absolute power then one of those two
Dialogue: 0,0:04:18.03,0:04:24.51,Default,,0000,0000,0000,,premises must be wrong. I'll come to the
Dialogue: 0,0:04:22.68,0:04:27.09,Default,,0000,0000,0000,,definition of inductive arguments in a
Dialogue: 0,0:04:24.51,0:04:28.98,Default,,0000,0000,0000,,moment, but first I want to point out two
Dialogue: 0,0:04:27.09,0:04:33.12,Default,,0000,0000,0000,,interesting features of deductive
Dialogue: 0,0:04:28.98,0:04:36.48,Default,,0000,0000,0000,,arguments: First if you use deductive
Dialogue: 0,0:04:33.12,0:04:40.08,Default,,0000,0000,0000,,arguments you can't make any new
Dialogue: 0,0:04:36.48,0:04:42.24,Default,,0000,0000,0000,,mistakes. The only way for the conclusion
Dialogue: 0,0:04:40.08,0:04:45.78,Default,,0000,0000,0000,,of a deductive argument to be false is
Dialogue: 0,0:04:42.24,0:04:47.97,Default,,0000,0000,0000,,if one of your assumptions is false, so
Dialogue: 0,0:04:45.78,0:04:50.31,Default,,0000,0000,0000,,if you already believe something false
Dialogue: 0,0:04:47.97,0:04:52.94,Default,,0000,0000,0000,,then your conclusion may end up being
Dialogue: 0,0:04:50.31,0:04:56.61,Default,,0000,0000,0000,,false. But if your assumptions are true
Dialogue: 0,0:04:52.94,0:04:57.57,Default,,0000,0000,0000,,your conclusions are guaranteed to be
Dialogue: 0,0:04:56.61,0:05:00.93,Default,,0000,0000,0000,,true as well.
Dialogue: 0,0:04:57.57,0:05:03.57,Default,,0000,0000,0000,,So deductive arguments never introduce
Dialogue: 0,0:05:00.93,0:05:06.06,Default,,0000,0000,0000,,falsehoods if they weren't already there.
Dialogue: 0,0:05:03.57,0:05:08.25,Default,,0000,0000,0000,,And that makes them very strong and good
Dialogue: 0,0:05:06.06,0:05:13.32,Default,,0000,0000,0000,,arguments to use, because they're not
Dialogue: 0,0:05:08.25,0:05:16.13,Default,,0000,0000,0000,,very risky. Second logicians found out
Dialogue: 0,0:05:13.32,0:05:18.18,Default,,0000,0000,0000,,already more than 2,000 years ago--and
Dialogue: 0,0:05:16.13,0:05:20.88,Default,,0000,0000,0000,,Aristotle played an important role here--
Dialogue: 0,0:05:18.18,0:05:23.82,Default,,0000,0000,0000,,that whether a deductive argument is
Dialogue: 0,0:05:20.88,0:05:26.13,Default,,0000,0000,0000,,valid or not can be determined just by
Dialogue: 0,0:05:23.82,0:05:29.46,Default,,0000,0000,0000,,looking at the form of the argument and
Dialogue: 0,0:05:26.13,0:05:32.61,Default,,0000,0000,0000,,ignoring its content. Even if you know
Dialogue: 0,0:05:29.46,0:05:35.43,Default,,0000,0000,0000,,nothing about medieval kings and Louis 7
Dialogue: 0,0:05:32.61,0:05:39.39,Default,,0000,0000,0000,,you can still see that our example
Dialogue: 0,0:05:35.43,0:05:44.55,Default,,0000,0000,0000,,argument is valid. How? Because there's
Dialogue: 0,0:05:39.39,0:05:47.94,Default,,0000,0000,0000,,this form: No A is B. C is A. So C is not B.
Dialogue: 0,0:05:44.55,0:05:51.60,Default,,0000,0000,0000,,Where A is "medieval King," B is "someone
Dialogue: 0,0:05:47.94,0:05:53.67,Default,,0000,0000,0000,,with absolute power," and C is "Louis 7" But
Dialogue: 0,0:05:51.60,0:05:55.47,Default,,0000,0000,0000,,we can put anything we like in the place
Dialogue: 0,0:05:53.67,0:05:58.50,Default,,0000,0000,0000,,of those letters and the argument will
Dialogue: 0,0:05:55.47,0:06:02.07,Default,,0000,0000,0000,,remain valid. For instance, let's choose A
Dialogue: 0,0:05:58.50,0:06:05.19,Default,,0000,0000,0000,,"Is a Dutchman" B "is humble" and C "is Victor
Dialogue: 0,0:06:02.07,0:06:07.26,Default,,0000,0000,0000,,or Gijsbers" Then we have: No Dutchman
Dialogue: 0,0:06:05.19,0:06:10.05,Default,,0000,0000,0000,,is humble. Victor Gijsbers is a
Dialogue: 0,0:06:07.26,0:06:12.84,Default,,0000,0000,0000,,Dutchman. So Victor Gijsbers is not
Dialogue: 0,0:06:10.05,0:06:15.27,Default,,0000,0000,0000,,humble. Which is another valid argument.
Dialogue: 0,0:06:12.84,0:06:18.72,Default,,0000,0000,0000,,Although of course the first premise is
Dialogue: 0,0:06:15.27,0:06:20.61,Default,,0000,0000,0000,,false and so is the conclusion. So we can
Dialogue: 0,0:06:18.72,0:06:22.80,Default,,0000,0000,0000,,see whether a deductive argument is
Dialogue: 0,0:06:20.61,0:06:24.84,Default,,0000,0000,0000,,valid simply by looking at its form
Dialogue: 0,0:06:22.80,0:06:27.81,Default,,0000,0000,0000,,without knowing anything about its
Dialogue: 0,0:06:24.84,0:06:30.00,Default,,0000,0000,0000,,content. And that is really important
Dialogue: 0,0:06:27.81,0:06:31.91,Default,,0000,0000,0000,,because that means that we can see
Dialogue: 0,0:06:30.00,0:06:35.37,Default,,0000,0000,0000,,whether something is a good argument
Dialogue: 0,0:06:31.91,0:06:38.15,Default,,0000,0000,0000,,without making any prior theoretical
Dialogue: 0,0:06:35.37,0:06:40.86,Default,,0000,0000,0000,,assumptions about the content matter. If
Dialogue: 0,0:06:38.15,0:06:42.87,Default,,0000,0000,0000,,we believe that scientists first
Dialogue: 0,0:06:40.86,0:06:44.52,Default,,0000,0000,0000,,collect data and then come to a
Dialogue: 0,0:06:42.87,0:06:47.31,Default,,0000,0000,0000,,conclusion about which theories are
Dialogue: 0,0:06:44.52,0:06:50.61,Default,,0000,0000,0000,,right and wrong, this is exactly what we
Dialogue: 0,0:06:47.31,0:06:53.34,Default,,0000,0000,0000,,would expect. We only need the data and
Dialogue: 0,0:06:50.61,0:06:56.19,Default,,0000,0000,0000,,some valid arguments which can be shown
Dialogue: 0,0:06:53.34,0:06:58.77,Default,,0000,0000,0000,,to be valid independent of any theories
Dialogue: 0,0:06:56.19,0:07:02.61,Default,,0000,0000,0000,,or ideas, and then we draw our
Dialogue: 0,0:06:58.77,0:07:08.07,Default,,0000,0000,0000,,conclusions. It would be great if science
Dialogue: 0,0:07:02.61,0:07:09.56,Default,,0000,0000,0000,,worked like that. Unfortunately, and I bet
Dialogue: 0,0:07:08.07,0:07:13.20,Default,,0000,0000,0000,,you saw that coming,
Dialogue: 0,0:07:09.56,0:07:14.76,Default,,0000,0000,0000,,science doesn't work like that. And it
Dialogue: 0,0:07:13.20,0:07:17.34,Default,,0000,0000,0000,,doesn't work like that because the most
Dialogue: 0,0:07:14.76,0:07:21.96,Default,,0000,0000,0000,,important arguments in science are not
Dialogue: 0,0:07:17.34,0:07:23.91,Default,,0000,0000,0000,,deductive. They are inductive. Remember
Dialogue: 0,0:07:21.96,0:07:26.39,Default,,0000,0000,0000,,that a deductive argument is an argument
Dialogue: 0,0:07:23.91,0:07:29.10,Default,,0000,0000,0000,,such that the truth of the premises
Dialogue: 0,0:07:26.39,0:07:33.15,Default,,0000,0000,0000,,absolutely guarantees the truth of the
Dialogue: 0,0:07:29.10,0:07:34.59,Default,,0000,0000,0000,,conclusion. An inductive argument is an
Dialogue: 0,0:07:33.15,0:07:36.66,Default,,0000,0000,0000,,argument where the truth of the premises
Dialogue: 0,0:07:34.59,0:07:39.72,Default,,0000,0000,0000,,gives good reason to believe the
Dialogue: 0,0:07:36.66,0:07:43.56,Default,,0000,0000,0000,,conclusion but does not absolutely
Dialogue: 0,0:07:39.72,0:07:44.30,Default,,0000,0000,0000,,guarantee its truth. Again let's look at
Dialogue: 0,0:07:43.56,0:07:46.83,Default,,0000,0000,0000,,an example:
Dialogue: 0,0:07:44.30,0:07:49.14,Default,,0000,0000,0000,,None of the medieval texts we have
Dialogue: 0,0:07:46.83,0:07:52.77,Default,,0000,0000,0000,,studied argues against the existence of
Dialogue: 0,0:07:49.14,0:07:55.61,Default,,0000,0000,0000,,God, so no scholar in the Middle Ages
Dialogue: 0,0:07:52.77,0:07:58.77,Default,,0000,0000,0000,,argued against the existence of God.
Dialogue: 0,0:07:55.61,0:08:00.63,Default,,0000,0000,0000,,That's a valid argument if it's true
Dialogue: 0,0:07:58.77,0:08:03.12,Default,,0000,0000,0000,,that none of the texts we have makes
Dialogue: 0,0:08:00.63,0:08:05.88,Default,,0000,0000,0000,,this argument, and we have a lot of texts,
Dialogue: 0,0:08:03.12,0:08:08.21,Default,,0000,0000,0000,,and it's quite plausible that nobody in
Dialogue: 0,0:08:05.88,0:08:12.39,Default,,0000,0000,0000,,that time actually made this argument.
Dialogue: 0,0:08:08.21,0:08:14.58,Default,,0000,0000,0000,,But it's indeed only plausible. It could
Dialogue: 0,0:08:12.39,0:08:18.45,Default,,0000,0000,0000,,be that the argument was made but
Dialogue: 0,0:08:14.58,0:08:20.97,Default,,0000,0000,0000,,somehow it wasn't transmitted to us. So
Dialogue: 0,0:08:18.45,0:08:23.09,Default,,0000,0000,0000,,in an inductive argument. The truth of
Dialogue: 0,0:08:20.97,0:08:26.58,Default,,0000,0000,0000,,the premises makes the conclusion likely,
Dialogue: 0,0:08:23.09,0:08:29.22,Default,,0000,0000,0000,,but it doesn't guarantee it. And that's
Dialogue: 0,0:08:26.58,0:08:31.56,Default,,0000,0000,0000,,generally the case in science. We have
Dialogue: 0,0:08:29.22,0:08:34.14,Default,,0000,0000,0000,,some limited data. We want to draw a
Dialogue: 0,0:08:31.56,0:08:36.57,Default,,0000,0000,0000,,general conclusion from those, and our
Dialogue: 0,0:08:34.14,0:08:39.42,Default,,0000,0000,0000,,data makes the conclusion likely but
Dialogue: 0,0:08:36.57,0:08:41.79,Default,,0000,0000,0000,,they don't make it certain. So, in science,
Dialogue: 0,0:08:39.42,0:08:44.76,Default,,0000,0000,0000,,we are continually making inductive
Dialogue: 0,0:08:41.79,0:08:48.24,Default,,0000,0000,0000,,arguments. And, as we will see in the next
Dialogue: 0,0:08:44.76,0:08:52.46,Default,,0000,0000,0000,,lecture, induction is a lot more
Dialogue: 0,0:08:48.24,0:08:52.46,Default,,0000,0000,0000,,problematic than deduction.