Mental gymnastics to prepare to tackle Hume

1
Lecture 6

• Mental gymnastics to prepare to tackle Hume
• The Problem of Induction as Hume argues for it
• His question
• His possible solutions
• His conclusion
• Salmons illustration of the problem
• (By the way, do current evolutionary theory and
  cognitive science solve the problem?)
• Anticipating the reading by Carl Hempel

2
Logic puzzles

• Background Of the majors that score highest on
  the LSATs and GREs, Philosophy majors and double
  majors in Philosophy and a science are
  consistently in the highest group (or are the
  highest ranking group)
• Explanation the particular emphasis Philosophy
  places on logical reasoning and arguments.

3
Logic puzzles

• Guidelines for solving logic puzzles
• Take the information given as if written in
  stone.
• Pay attention to the question asked.
• Find the beginning of a thread one thing you can
  be sure of this is enables you to unravel the
  rest.
• In general, proceed from the first piece of
  information provided to the next
• Assume there is a correct answer and that it can
  be reached given the information provided.

4
A logic puzzle

• In a mythical (?) community, politicians always
  lie and non-politicians always tell the truth.
• An anthropologist meets 3 natives of the
  community. She asks the first native if she is a
  politician.
• The first native answers.
• The second native reports that the first native
  denied being a politician.
• The third native states that the first native is
  a politician.
• How many of these natives are politicians?

5
A logic puzzle

• Ground rule politicians always lie and
  non-politicians always tell the truth.
• The anthropologist asks the first native Are you
  a politician?
• Can we know what she answered, without relying on
  what the 2nd and 3rd natives say?
• What do we know about the 2nd native given what
  she said?
• And does she help us to figure out what the 1st
  native is?

6
A logic puzzle

• What can we know given the third natives claim
  about whether
• What can we know about the first native or the
  third is a politician?
• Recall the question
• Can we answer it?

7
A logic puzzle

• Yes. The first native, whether a politician or a
  non-politician, had to deny being one. We dont
  know what she is.
• We know that the second native is a
  non-politician because she reported the truth
  about what the first native said (and had to
  say).
• If the 3rd native is a politician, the first
  native is not. If the 3rd native is a
  non-politician, the first native is a politician.
• So there is one and only one politician.

8
Part II

• Hume on the
• Problem of Induction

9
Inductive reasoning

• For empiricists such as Hume, all the evidence
  there is for empirical knowledge (i.e., knowledge
  concerning matters of fact, including
  scientific knowledge), is sensory experience.
• For Hume, we achieve empirical knowledge by
  reasoning from individual experiences/singular
  statements to generalizations/universal
  statements using induction (and we certainly do
  this a lot).

10
Inductive reasoning

• Empirical generalizations (an argument form or
  type)
• On day D1, at time T1, a black raven was
  observed.
• On day D2, at time T2, another black raven was
  observed.
• .
• .
• On day Dn, at time Tn, yet anotherblack raven was
  observed.
• A non-black raven has never been observed.
• --------------------------------------------------
  ---------------------
• All ravens are black

11

• For some empiricists including Hume the only
  other (respectable) kind of reasoning is
  deductive
• And it involves what Hume calls relations of
  ideas
• The intuition here is that some sentences (such
  as 2 2 4) are true by definition (if we
  know what 2 and 4 mean, as well as what
  and mean, then we know the sentence is true)
  or by form (such as A rose is a rose).
• And if a sentence is the conclusion of an
  argument that is deductively valid and has all
  true premises, we know its conclusion is true as
  well (a sound argument). Mathematical theorems,
  as derived from axioms, are examples.
• Hume calls knowledge arrived at in this way
  demonstrative knowledge

12
Humes question

• What justifies our use of induction?
• Recall that for Hume, there are two places to
  look for a source of such justification
• Experience
• Reason
• So he proposes we explore each to see if we can
  discover what justifies inductive reasoning

13
Experience?

• Millions of ravens have been observed and all
  are black.
• A non-black raven has never been observed.
• --------------------------------------------------
  -------
• All ravens are black
• Empirical generalizations, like other forms of
  inductive arguments, are ampliative the
  conclusion goes beyond the premises. So, the
  truth of the premises does not guarantee the
  truth of the conclusion. There is a gap.
• Can we not say, though, that induction has
  worked in the past and currently works so it is
  justified?

14
Humes question

• Can experience justify our use of induction?
• Say, we argue
• Induction has worked in the past and present to
  allow us to predict events/phenomena.
• -------------------------------------------------
  -----------------
• So, induction will work in the future to allow
  us to predict events/phenomena and, thus, is
  justified.
• If this reasoning doesnt justify induction, why
  doesnt it?

15
Humes question

• Can reason (demonstrative knowledge) provide the
  justification?
• No.
• Because
• There is no necessary connection (as there is in
  2 2 4) between
• Ive always (and so has everyone else)
  experienced that X causes Y
• and
• The next X I encounter will cause Y

16
Humes question

• Can experience justify our use of induction?
• Maybe if we add a premise
• Say, we argue
• Induction has worked in the past and present to
  allow us to predict events/phenomena.
• Nature is uniform.
• -------------------------------------------------
  -------------------------
• So, induction will work in the future to allow
  us to predict events/phenomena.
• This is a deductively valid argument, so why
  cant it solve the problem of induction?

17
Humes question

• But what is the justification for this premise?

18
Humes conclusions

• If its not justified, then why do we engage in
  inductive reasoning?
• And can we avoid engaging in inductive reasoning
  if Hume is correct about why we do?
• His conclusion about induction is a skeptical
  one but what is the nature of the skepticism?
• And what are the implications of the problem of
  induction (which, though many have claimed to
  solve it, has in fact no solution) for science?

19
Part III

• Salmons poor physics student

20
Salmons physics studentwho is also studying
Hume!

• So this poor student is learning about some laws
  of nature , and having them demonstrated to him,
  in his physics class and labs but also
• Learning from his Philosophy Prof and TA that
  these laws (because they are empirical and they
  are generalizations) not only cant be proven but
  its irrational (according to Hume) to believe in
  them

21
Salmons physics studentwho is also studying
Hume!

• Perhaps predictably, the student assumes that
  Humes arguments date to a time when what he
  (Hume) calls secret powers somehow connecting
  each event A with an event B were not yet known.
  So its simply a historical piece without current
  relevance (and so he asks, Why am I asked to
  read this at all??)
• Is he right? Why or why not?

22
Salmons physics studentwho is also studying
Hume!

• Second hypothesis Humes problem is not any
  longer a problem because since his time, we have
  discovered many laws of nature conservation of
  energy, conservation of momentum, etc. which
  allow us to predict (correctly) the outcome of
  any and all relevant experiments and occurrences.
• What does he learn from his professors in each
  discipline about the status of the laws of nature?

23
The physics students professors

• His philosophy TA did your physics professor say
  that the laws of conservation of energy and
  momentum are, by their nature, inviolable, or
  that there are no known exceptions?
• His physics professors to whom he asks Is it
  possible that any or all of these laws will stop
  holding tomorrow or on some future date?
• Their answer

24
Part IV

• Carl Hempel and
• Sophisticated Inductivism

25
What do to with/about the problem of induction in
accounts of science?

• Hempel argues against and offers an alternative
  to what he calls narrow inductivism (others of
  us call this naïve inductivism)
• Uses a case study to illustrate what he thinks is
  a model of scientific reasoning
• What lessons does he draw from the case?
• And be sure to understand what he means by
  narrow and sophisticated inductivism