Transcript inductive reasoning

F34PPP Lecture 2:
Wrong, not even wrong, or good enough?
Philip Moriarty
School of Physics & Astronomy
[email protected]
@Moriarty2112
www.nottingham.ac.uk/physics/research/nano
Last time…
Science is more than just a driver of
technological/economic growth
 Seeing is believing? How objective is our
evidence?
 Logic and reason – deduction and valid
arguments

Logic and reason
“Logic is the study of reasoning abstracted from
what that reasoning is about.” [Ladyman]

All dachshunds are good physicists.
Daisy is a dachshund.
Therefore Daisy is a good physicist.
Both are valid
deductive arguments!
Invalid but not necessarily bad argument…
Moriarty claims to be a physicist
I have no reason to believe he is lying
Therefore Moriarty is a physicist
Both premises could be true
but conclusion could be false
– invalid deductive argument.
Today
Bacon and inductivism
 Is science really “organised scepticism”?
 The scientific method
 Popper and falsification

Objective evidence?
How do you know?
Have you taken the
measurements, analysed
the raw data, compared
theory with the
experimental results,
coded the simulations?
Just a matter of faith?
Aristotle vs Bacon
Aristotle – first formal study of logic.
 Aristotelian logic entirely revolves around
deductive reasoning.
 He has very little to say on inductive
reasoning, i.e. arguing from “the particular
to the universal”
 Inductive reasoning is “reasoning in which

the premises seek to supply strong
evidence for (not absolute proof of) the
truth of the conclusion. “ [Wikipedia]

No place for experimentation in Aristotle’s
logic.
Novum organum scientiarum


“New”, as opposed to Aristotle’s
old Organon
Organised scepticism
 Aristotelian methods too
biased – “anticipation of
Nature”
Objective and unbiased?
Millikan’s Manipulation?
Millikan’s Manipulation?
But Millikan’s notebooks show that 175 drops
were measured, with many measurements rejected
because they didn’t “meet expectations”….
“This is almost exactly right & the best one I
ever had!!! [20 December 1911]
Exactly right [3 February 1912]
Publish this Beautiful one [24 February 1912]
Publish this surely / Beautiful !! [15 Mar1912]
Error high will not use [15 March 1912, #2]
Perfect Publish [11 April 1912]
Won't work [16 April 1912, #2]
Too high by 1½% [16 April 1912, #3]
1% low
Too high e by 1¼%”
“Flirting with Fraud: Millikan, Mendel and the Fringes of Integrity”
-- https://www1.umn.edu/ships/ethics/millikan.htm
M. Niaz, J. Res. Sci. Teching 37 480 (2000)
“It’s a thing that scientists are ashamed of…”
“It's
interesting
to look
at thethe
history
of
“Why
didn't they
discover
new number
measurements
ofaway?
the charge
an that
was higher right
It's a of
thing
electron,
Millikan.of--this
If you plot
scientistsafter
are ashamed
history-them
as ait's
function
of time,
you find
because
apparent
that people
didthat
things
one
a little
bit bigger
than
Millikan's,
likeisthis:
When
they got
a number
that was
and
one's
a little bitthey
bigger
than
too the
highnext
above
Millikan's,
thought
that,
and themust
nextbe
one's
a little bitthey
bigger
something
wrong--and
would
than
untilfind
finally
they settle
down
lookthat,
for and
a reason
why something
tomight
a number
whichWhen
is higher.”
be wrong.
they got a number
close to Millikan's value they didn't look so
hard. And so they eliminated the numbers
that were too far off, and did other things
like that. We've learned those tricks
nowadays, and now we don't have that kind
of a disease.”
Hmmm…
Back to Bacon…
The Idols of the Mind
Idols of the Tribe – seeing order/patterns
where there are none (cf “patternicity”!);
wishful thinking; jumping to conclusions.
Idols of the Cave – personal/ideological
preferences.
Idols of the Marketplace – fallacies in
reasoning due to jargon and language.
(Nothing to do with markets in “free market”
sense, but we’ll come back to that topic…)
Idols of the Theatre – being wedded to a
particular (philosophical) framework.
Bacon’s Inductivism
- Observation followed by
Induction.
- Bacon argues that observation
must be based on methods
which minimise the influence of
the four idols.
- Generate set of observations.
- Use these observations as basis
of generalisations – scientific
laws. (e.g. F=GmM/r2 , PV =
nRT, Snell’s law etc..etc..)
“Man, as the minister and interpreter of nature,
is limited in act and understanding by his
observation of the order of nature; neither his
understanding nor his power extends further.”
Induction and Bacon
-
-
Induction: deductively invalid but
persuasive argument.
Observation without bias or
prejudice (!)
Instruments should eliminate the
role of the “unreliable senses”
Induction (in sense Bacon used
term) is generalisation from N
cases to all cases…
Bacon’s Inductivism – Some problems
-
-
We don’t really do experiments with no preconceived ideas,
do we?
Nor do we completely disregard expertise (Idol of the
Theatre). Is science truly underpinned by a “belief in the
ignorance of experts”?
..and does Bacon’s inductivism actually work?
David Hume
-
An empiricist (along with Locke, Berkeley)
Argues that Bacon’s inductive reasoning is “not really
reasoning at all, but rather merely a habit or a psychological
tendency to form beliefs about what has not yet been
observed on the basis of what has already been observed.”
[Ladyman, p.40]
When the sun goes down…
…how do we know it will rise again tomorrow
morning?




Logically possible that sun won’t rise tomorrow.
Justification for sun rising tomorrow (or ball
falling to ground when dropped) is on basis of
experience
But we assume that the future will be the same as
the past
Justified by logic? No. Logically possible for
future to be different from past.
David Hume
-
An empiricist (along with Locke, Berkeley)
Argues that Bacon’s inductive reasoning is “not really
reasoning at all, but rather merely a habit or a psychological
tendency to form beliefs about what has not yet been
observed on the basis of what has already been observed.”
[Ladyman, p.40]
-“May we venture to hope that when Bacon's next
centenary is celebrated the great work which he set going
will be completed; and that Inductive Reasoning, which
has long been the glory of Science, will have ceased to be
the scandal of Philosophy?” [CD Broad, 1887 – 1971]
Inductive arguments
“The very expression “scientifically
proven” is a contradiction in terms.
There’s nothing that is scientifically
proven. The core of science is the
deep awareness that we have wrong
ideas, we have prejudices.
…we have a vision of reality that is
effective, it’s good, it’s the best we
have found so far. It’s the most
credible we have found so far; it’s
mostly correct.”
Carlo Rovelli
http://www.newrepublic.com/article/118655/theoreticalphyisicist-explains-why-science-not-about-certainty
…but “mostly correct” can be more than good enough
Suggested blog post topics [300 – 500 words, 10%]
-
-
Should scientists have to justify their research
in terms of its socioeconomic impact?
Do social media have a role to play in the
scientific process?
When should scientists “go public” with their
results?
Are prizes like the Longitude Prize the future
of research funding?
Can science be crowd-funded?
Is peer review working?
Should universities cut back on funding of
PhD positions?
Is Richard Dawkins closed-minded?