Explanation in Science

Anuj Vijay BhatiaInstitute of Rural Management Anand

Fellow Participant

“Among the divers factors that have encouraged and sustained scientific inquiry through its long history are two pervasive human concerns which provide, I think, the basic motivation for all scientific research. One of these is man’s persistent desire to improve his strategic position in the world by means of dependable methods for predicting and, whenever possible, controlling the events that occur in it…”

CarlHempel

“…But besides this practical concern, there is a second basic motivation for the scientific quest, namely, man’s insatiable intellectual curiosity, his deep concern to know the world he lives in, and to explain, and thus to understand, the unending flow of phenomena it presents to him.”

CarlHempel

Other philosophers say:

“Theories are the crown of science, for in them our understanding of the world is expressed. The function of theories is to explain.”

Rom Harre, The Philosophies of Science, 1985“What is crucial is the insight that the kind of knowledge science produces...permits the development of explanations, and it is those explanations which are the real payoff.”

Joseph Pitt, Theories of Explanation, 1988

Quine & Ullian (1970)

“… the hypotheses we seek in explanation of past observations serve again in the prediction of future ones. Curiosity thus has survival value, despite having killed a cat.”

W.V.O. Quine & J.S. UllianThe Web of Belief (1970)

Heider (1958)

“If I find sand on my desk, I shall want to find out the underlying reason for this circumstance. I make this inquiry not because of idle curiosity, but because only if I refer this relatively insignificant offshoot event to an underlying core event will I attain a stable environment and have the possibility of controlling it.”

Fritz HeiderThe Psychology of Interpersonal Relations (1958)

Quick Recap

• Theories serve the function of:– Prediction– Intervention– Explanation

• But is explanation intrinsically valuable?• Perhaps explanation contributes to fulfilling

the other functions of theories, .e.g. prediction.

Hempel’s Covering Law Model of Explanation

• Scientific Explanations are given in response to ‘Explanation Seeing WHY questions’.

• To give explanations is to provide satisfactory answer to these questions.

• Scientific Explanations should have logical structure of argument

• A set of premises followed by a conclusion

Followed by Conclusion

Phenomenon that needs explanation actually occursSugar dissolves in Water

A Set of Premises

Why Conclusion is True

A Premise why sugar dissolves in water

Task of Scientific Explanation is the task of characterizing the relation between premises and conclusion. Premises count as explanation for conclusion.

Hempel’s answer to the problem is three-fold:

1. Premises should entail the conclusion (deductive)2. Premises should be true3. Premises should consist of at least one general law.

General laws are sometimes called the laws of nature.

To explain means to show that the occurrence of any phenomenon follows deductively from a general law, perhaps supplemented by other laws and/or particular facts, all of which must be true.

Why Plant on My Desk Died?

Poor sunlight in my study

No sunlight reaching the plant

No Photosynthesis

Plant on my desk dies

Death of plant is deduced from 2 laws:1. Sunlight is necessary for photosynthesis2. Photosynthesis is necessary for survivalAnd 1 particular fact:Plant was not getting sunlightHence, Plant diedSchematically,General LawsParticular facts Phenomenon to be explained

Premises

Conclusion

Explanans

Explandum

Explanation and Prediction“Two Sides of The Same Coin”

• Every Scientific Explanation is a potential prediction (Hempel)

• Explanation predicts phenomenon, if we hadn’t known about it.

• Converse is also true: Every reliable prediction is potentially an explanation.

• Example: Mountain Gorilla will extinct by 2020• Explanation and Prediction are structurally

symmetric

Counter Examples to Covering Law

Type 1: Scientific Explanations that do not fit the covering law• Model is too strict• Excludes bona fide scientific explanations

Type 2: Cases that fit the covering law, but intuitively do not fit as genuine scientific explanations• Too Liberal• Allows things that should be excluded

The Problem of Symmetry

General Laws Light Travels in Straight LinesLaws of Trigonometry

Particular fact Angle of elevation of the sun is 37˚Flagpole is 15 meters high

Phenomenon to be explained: Shadow is 20 meters long

Suppose we swap the explandum General Laws Light Travels in Straight Lines

Laws of TrigonometryParticular fact Angle of elevation of the sun is 37˚

Shadow is 20 meters longPhenomenon to be explained: Flagpole is 15 meters high

Explanation confirms covering law pattern.The height of flagpole is deduced from the length of shadow.But why is flagpole 15 meters high?? – Nothing do with the length of shadowHence, Hempels model is too liberal, does not respect assymetry

The Problem of Irrelevance“ Why is John not Pregnant???”

Doctor: “John has been taking birth control pills. People who take birth control pills regularly never becomes pregnant.”Suppose, John actually takes birth control pills.Hence, John has not become pregnant.(But this is not the correct explanation, John is male, he cannot be pregnant)Here,• General Law is true• Particular Fact is True• But, because of this John is not pregnant – not a valid explanation.Covering law allows things to count as scientific explanation, which are intuitively not.Doctors explanation to child is irrelevant: John would not have been pregnant even if he had not taken birth control pills.

Explanation and Causality• Problems in Covering Law: Need for Alternative• Some Philosophers favoured Causality• Many times covering law is same as causality• In some cases, its not.

Example: 20 mtr shadow does not explain why flagpole is 15 mtrs high.

• Accommodates asymmetric relations– X causes Y, but Y does not Cause X

• Do not run the problem of irrelevance• But it cannot be the whole story: H20 is Water

– This explanation is not causal

Can Science Explain Everything?

• No. – Example: Origin of Life

• No reason to think that it will be never explained.• No guarantee that it will be explained.• Newtonian Science: Law of gravity is a

fundamental principle– It cannot explain itself– It may remain unexplained.

Explanation and Reduction

• Different disciplines of science explains different phenomenon.

• They are not in competition with each other• They are not at par too– Some are more fundamental than others.

(Physics)

Multiply Realized• Will physics be able to explain things that biology or economics

explain? • How can a science that studies entities that are ultimately

physical not be reducible to physics?– Answer: Multiple Realization– Example : Ashtrays of various kinds

• We cannot say ‘X is an ashtray if and only if……..”• This means ashtrays are multiply realized at physical level

• Psychology cannot be reduced to physics or chemistry (works for higher-level sciences)– Physics cannot explain why nerve cells live longer than skin cells.– Not all philosophers are happy about this– But still a neat explanation of the autonomy of higher-level

sciences, both from physics and from each other.