Induction, Deduction, and the Scientific Method - Irving Rothchild.pdf - Revolucja w NAUCE - LORDANIME

INDUCTION, DEDUCTION, AND THE SCIENTIFIC METHOD

AN ECLECTIC OVERVIEW OF THE PRACTICE OF SCIENCE

I RVING R OTHCHILD

Emeritus Professor of Reproductive Biology

Case Western Reserve University School of Medicine

Cleveland, Ohio

CONTENTS

ABSTRACT 1

INTRODUCTION 1

INDUCTION AND DEDUCTION 2

Etymology 2

De ini ions 2

Induction 2

Deduction 3

THE SCIENTIFIC METHOD 3

BEING A SCIENTIST 4

Making Observa ions 4

Point of View 5

Asking the Right Ques ion 6

Theorizing 6

The theory (or finding) that questions authority 7

Defending the controversial theory or finding 8

Eurekas 8

Expe imenta ion 9

The failed experiment 9

Publishing 10

Sta is ics 10

Recogni ion 10

ACKNOWLEDGEMENTS 10

REFERENCES 11

INDUCTION, DEDUCTION, AND THE SCIENTIFIC METHOD

AN ECLECTIC OVERVIEW OF THE PRACTICE OF SCIENCE

I RVING R OTHCHILD *

Emeritus Professor of Reproductive Biology

Case Western Reserve University School of Medicine

Cleveland, Ohio

ABSTRACT: Science is a never-ending, always changing process through which we learn to

know the material nature of the universe. Science does not deal with nonmaterial entities such as

gods, for there is no way their existence can be either proved or disproved. No single, identifiable

method applies to all branches of science; the only method, in fact, is whatever the scientist can

use to find the solution to a problem. This includes induction, a form of logic that identifies

similarities within a group of particulars, and deduction, a form of logic that identifies a particular

by its resemblance to a set of accepted facts. Both forms of logic are aids to but not the solution

of the scientist’s problem.

Being a good scientist requires patience, perseverance, imagination, curiosity, and skepticism;

the essence of science is to doubt without adequate proof. Science also requires knowing how to

make and interpret observations (which presupposes a broad point of view), how to ask the right

questions, how to theorize without getting lost in the details, and knowing when to do

experiments and apply statistical tests. Recognition of one’s work is desirable but should not be

the primary goal, and publishing papers should be used primarily as a test of the scientist’s ability

to pursue good science.

*Correspondence: ssradmin@ssr.org

INTRODUCTION

In an essay entitled Is the Scientific Paper a Fraud?

[1], Peter Medewar claimed that induction, in contrast

to deduction, had no place in science. His implication

of fraud was aimed, not at the paper’s contents, but at

how they were presented, and here he strongly implied

that this presentation was an inductive process. Mede-

war was a great admirer of Karl Popper, a philosopher

of science. In The Logic of Scientific Discovery [2],

Popper rejected induction as a legitimate form of logic

in the practice of science. To bolster his argument a-

gainst induction in science, Medewar cited an unsuc-

cessful attempt by John Stuart Mill to solve problems

in sociology by induction, but neglected to mention

Francis Bacon’s contribution to the birth of modern

science in the 17th century by the use of induction as a

powerful alternative to Aristotelian and scholastic

dogma.

Popper and Medewar argued vehemently for a

method of scientific practice based on the so-called

hypothetico-deductive system, the essence of which is

the formulation of a hypothesis derived from a collec-

tion of facts, testing the hypothesis by trying to ‘falsi-

fy’ it, collecting more facts if ‘falsification’ fails, and

repeating the falsification tests until either you and the

hypothesis agree on a draw or one of you admits de-

feat. Medewar (1915–1987) shared the 1960 Nobel

Prize in Medicine or Physiology with Sir Frank Mac-

Farlane for their work on the mechanism of tolerance

to acquired immunity. Karl Popper (1902–1994) was

knighted by Queen Elizabeth II in 1965 and elected a

Fellow of the Royal Society in 1976, so there’s no

question here about the kinds of minds we’re dealing

with.

It is perhaps not too hard to understand that a phil-

osopher, even of science, could make judgments about

any aspect and especially the methods of science, but

what confuses me and I’m sure would confuse any

graduate student or postdoc or, in fact, anyone with an

inquiring mind is why someone like Medewar, a prac-

ticing scientist, and certainly no dummy, should get

worked up enough about induction to write an essay

excommunicating it from the scientific community. Is

it really that wicked? Or useless? Should I, as a grad-

uate student, watch my step to make sure I don’t ever

use induction in my research? Can I still become a sci-

ROTHCHILD

entist if I do? Should I be careful to use only deductive

reasoning and not lift a finger to make my next ad-

vance into knowledge without first having formulated a

hypothesis? What if I just want to ask a question?

Medewar’s essay and Popper’s philosophy of sci-

ence are a good example of an idiosyncratic viewpoint

about what science is and how it should be practiced. It

is not my own point of view. The purpose of this essay

is to make three main points that emerge from this dif-

ference. The first is that induction is an integral part of

the practice of science and Propper and Medewar,

therefore, in spite of their membership in the class of

intellectual giants, are not only talking nonsense about

induction having no place in science, but are com-

mitting a logical heresy by doing so. The next is that

scientific methods such as hypothetico-deductive [1],

Koch’s postulates [3], or any other system based on

rules of procedure or analysis, while they may be legit-

imate ways to practice science, are far from the only

ways to do so. The final point is that certain features of

the practice of science, theorizing, for example, are

essential parts of all branches of science and far more

important than searching for a non-existent only true

“scientific method.” Most of what I have to say should

be seen only as a perspective of my own ideas about

how we practice science, arising from my familiarity

with the practical and theoretical methods of science,

or having read or heard about or observed being used

by other scientists. Most (if not all) of this has been

said before but that doesn’t matter. Each viewpoint,

like each human being, is different and the differences

can sometimes be more interesting than the similar-

ities. A close friend and colleague, for example, disa-

grees with my definition of science! That’s the point.

There is no consensus, even among scientists, about

exactly what science is and every viewpoint, therefore,

can be at least potentially, valuable. It hardly needs

saying that the views expressed in this essay are not

necessarily those of the SSR or its Web site.

Before we get into the nitty-gritty of this essay,

however, a small light touch may help to set the stage,

especially since it serves very well as a pleasant ex-

ample of what science can be all about. In a charming

essay entitled Can an Ape Tell a Joke? [4], Vickie

Hearn describes a problem-solving study in which a

chimpanzee and an orangutan, housed separately, were

each given a small hexagonal block of wood and an

assortment of differently shaped openings into only

one of which the block would fit. They knew they

would be rewarded for making the right choice.

The chimp examined every detail of the floor,

walls, and ceiling; the openings and every side of the

hexagonal block; smelled it, tasted it, and, after trying

one opening after another, found one the block would

fall into. The orangutan scratched his back with the

block, and then sat with a far away look in his eyes for

what seemed to the human observer like forever. He

then put the block directly into the hexagonal opening.

Was the chimp an inductivist? Did the orangutan

consider the problem, form a hypothesis, then test it?

Which one was the scientist? Let’s reserve the answer

for the section below called THE SCIENTIFIC

METHOD.

INDUCTION AND DEDUCTION

A commonly held idea of the distinction between

these logical paths to knowledge is that induction is the

formation of a generalization derived from examina-

tion of a set of particulars, while deduction is the iden-

tification of an unknown particular, drawn from its re-

semblance to a set of known facts. For example, if we

examine enough feral cats we can generalize that feral

cats are a rich sources of fleas (induction). If, like Rob-

inson Crusoe, we come across footprints on the beach

of a desert island, we can conclude from our know-

ledge of the human footprint that another human is or

was on the island (deduction).

In fact, however, both terms can have more subtle

meanings. Let’s start with a look at their etymology

and definitions.

Etymology

The etymology of these words does not seem to

have any of the judgmental qualities attributed to them

by Popper and Medewar. They come from the Latin

verb ducere , to draw on or along, to pull or drag, to

draw to oneself, to lead, and with the Latin propensity

for prefixes. suffixes, and the modification of the verb

itself, ducere has spawned an enormous population of

derivatives [5]. Even with only the prefixes in and de ,

meaning ‘in’ and ‘from,’ respectively, both words may

have many more than one meaning. Simply put, to

induce could mean ‘to lead or draw into, to infer, to

persuade,’ and induction , ‘to lead to the conclusion that

etc....’ To deduce could mean ‘to lead from, to draw

from’ and deduction , ‘to draw a conclusion from etc....’

The official lexicographic and practical definitions are

not always much more distinctive.

Definitions

Induction . From The Oxford English Dictionary

( OED ); to induce (in relation to science and logic)

means “to derive by reasoning, to lead to something as

a conclusion, or inference, to suggest or imply,” and

induction “as the process of inferring a general law or

principle from observation of particular instances.”

Another version is the “adducing (pulling together) of

INDUCTION, DEDUCTION, AND THE SCIENTIFIC METHOD

a number of separate facts, particulars, etc. especially

for the purpose of proving a general statement.”

My 1967 edition of the Encyclopedia Britannica ( E.

Brit. ) gives two versions by John Stuart Mill: “the

operation of discovering and proving general proposi-

tions” or “that operation of the mind by which we infer

that what we know to be true in a particular case or

cases will be true in all cases that resemble the former

in certain assignable respects.”

A paraphrase of Francis Bacon’s view (also from

the E. Brit. ) is “a selective process of elimination

among a number of alternative possibilities.”

The E. Brit. in a separate entry defines primary

induction as “the deliberate attempt to find more laws

about the behavior of the thing that we can observe and

so to draw the boundaries of natural possibility more

narrowly” (that is, to look for a generalization about

what we can observe), and secondary induction as “the

attempt to incorporate the results of primary induction

in an explanatory theory covering a large field of

enquiry” (that is, to try to fit the generalization made

by primary induction into a more comprehensive

theory).

E. Mayr in his Growth of Biologic Thought [6]

offers this definition: “inductivism claims that (we) can

arrive at objective unbiased conclusions only by…

recording, measuring, and describing what we encoun-

ter without any root hypothesis….”

Deduction. Sherlock Holmes’ “Elementary, my

dear Watson!” has made deduction common know-

ledge a more familiar feature than induction in problem

solving. The OED definition of to deduce is “to show

or hold a thing to be derived from etc...” or “to draw as

a conclusion from something known or assumed, to

infer”; deduction thus is “inference by reasoning from

generals to particulars,” or “the process of deducing

from something known or assumed...”

Both terms define systems of logic the purpose of

which is to solve problems, in the one case by looking

for a general characteristic (generalization, conclusion,

conjecture, supposition, inference, etc.) in a set or

group of observations, in the other to identify a particu-

lar instance through its resemblance to a set or group of

known instances or observations. Popper’s ridicule of

induction was based on the premise that induction re-

quires the observation of every instance of a given

phenomenon for the generalization to be true—an

obvious impossibility; the fact that all known crows are

black, for example, doesn’t prove that no white crows

exist. Of course it is ridiculous when looked at in this

way, but what really matters is that most if not all

crows are black, and even if a white one should show

up and prove to be a crow and not another kind of bird,

most crows would still be black. His argument can also

be used to make deduction useless for it, too, is based

on an incomplete set of known facts. Even if the

identified fact resembles the members of the set, how

can we be sure that every possible feature of either the

unknown or the members of the set itself has been

considered? As we will see in what follows, in many of

the examples of the way science is practiced, induction

is as much a part of this practice as is deduction or any

system of logic that serves the purpose of advancing

knowledge. Induction and deduction are two, usually

different but never contradictory, approaches to prob-

lem solving. The problem must be solved by testing the

validity of the conclusion or inference, etc. reached

from either direction. Induction and deduction are thus

valuable, often complementary, tools that facilitate

problem solving.

THE SCIENTIFIC METHOD

In spite of what I have said so far, is there a

particular method we can call THE scientific method?

To answer this question it is essential that we first ask

another question: what do we mean by science? The

word comes from Latin scire , “to know,” and scire

comes from an earlier Latin root meaning “to cut

through,” i.e. to take apart, to analyze. But science is

more than just knowing by analysis. Science is a

process of learning to know the nature of everything in

the material world, from atoms to the most complex of

living organisms and inanimate objects. Nonmaterial

things, like gods, whose existence can be neither

confirmed nor disproved, are excluded, for science

deals only with those elements of the universe that can

be shown, at least potentially, to exist. Science,

therefore, is never-ending and always changing.

Although its goal is knowledge, it is more than and

different from knowledge itself, for knowledge is its

product not its essence. Its essence is to doubt without

adequate proof. Science is the offspring of philosophy,

and differs from it mainly in the methods used in

learning to know.

As with almost all systems of classification, we

can’t draw a sharp distinction between science, as

defined here, and other forms of scholarship as sources

of knowledge such as the OED , Grove’s Dictionary of

Music and Musicians , the Dickson Baseball Diction-

ary , etc. or even history, for example. In many

respects, history is a science but it is poorly endowed

with or even lacks the ability to predict, one of the

important things that separates science from other

forms of learning.

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