Hypothetico-Deductive Method of Science

Prologue

              The philosophers of science have been engaged, for a long, with the question of the scientific method and the pattern of reasoning that leads to a scientific theory. Equally important has been the issue of discovery vs. invention of scientific theory. There has been a long-drawn debate over the true nature of the scientific method. The two most prominent versions that present the nature of the scientific method are the inductionist version and the hypothetical version.
                 The hypothetical method of science is popularly known as hypothetico-deductive method of science that considers the role of creativity, deduction and falsification or empirical verification as the cornerstone of the scientific method as against the simple observational and inductive process highlighted by the inductionists. 

Dialogue

What are the assumptions of Inductivism? 

     Inductionism in science is based on three assumptions viz:

• Knowledge can be created by drawing inferences from a wide range of objective observations.

• The observer (scientist) makes observations in a detached way i.e. he or she is not influenced by their personal assumptions, theories or beliefs while making the observations. 

• All observations are done in a theoretical vacuum.

    What are the problems with these assumptions?

  The assumptions of inductivism are however considered as problematic. Two fundamental problems are raised against Inductivism. These are:

• The first problem with Inductive Method is that observations are considered as highly objective venture and that scientists make observations in a theoretical vacuum.  Darwin highlights this problem when he says  in one of his letters that 

How odd it is that anyone should not see that observations must be for or against some view if it is  to be of any service" (Darwin, 1903, Vol 1, p.195).

• The second challenge faced by Inductionism is popularly known as the “Problem of Induction”. We know that induction involves making inferences based on the large data collected through objective observations. It makes generalisations about some phenomena based on the observations. Now any such generalisation is never conclusive in Induction. However, large our data might be, it is never all-inclusive. Let’s see with an example.

        Based on observations it is generalised that all swans are white in colour. This 5generalisation is based on a large number of observations. However, yet not all swans have been observed. There is always a possibility that someday some black coloured swan might be observed. Even though the likelihood of such observation is very small, yet it can not be ruled out. This is popularly known as the problem of induction. 

Is inductivism totally rejected? 

       Thus simple induction is rejected as the normal method of science. Even though it is appropriate for simple scientific facts, it is ruled out as the means to arrive at complex scientific theories and explanations.

         Induction nevertheless plays a significant role in helping scientists come up with their bold conjectures. Even though observation is considered an essential aspect of scientific inquiry, the observation done is guided by prior notions of the scientist. Further, the generalisations arrived at involve more than simple induction from a large pool of observed data.

What are contemporary assumptions on the scientific method? 

             The contemporary belief is that all observations are theory laden. This means the scientists make guided observations. Observation do not occur in a theoretical vacuum and rather all observations are carried out against the scientists’ preconceived notions or assumptions or personal theories.

        Science make leaps through the intervention of the scientists’ prior theories or preconceived notions that in turn influence their decision regarding observations to be done. 

         Why is the term hypothetico used in HD Method? 

           According to Christian Huygens, the construction of a scientific theory begins with scientists' bold conjecture(s).  where conjectures are sort of explanations for some phenomenon. These conjectures are hypothetical in nature. 

         According to Whewell, all scientific theories begin with a hypothesis. The hypothesis is a conjectural statement about the relationship between two or more variables. This hypothesis is assumed to be a generalised statement that is created by the scientist to explain some phenomenon and is assumed to explain a wide range of observations It’s a bold gesture from the scientist based on their personal theories and preconceived notions.

       The creation of scientific knowledge begins with the scientist's conjecture (Hypothesis) which is an outcome of the creative ability of the scientists to "synthesize, to relate, and to formulate new conceptual structures" (Velasquez, 2007, p.227). 

           Whewell, further argued that                    

"Our hypotheses ought to foretell phenomena which have not yet been observed...    the truth and accuracy of these predictions were a proof ..  that the hypothesis was…..  valuable and, at least    to a great extent, true.                                                                       (Whewell 1847, 62-63).

Thus the scientific method is assumed to be hypothetical rather than inductive as was popularly presented.

Why us the term deductive used in HD Method?

        The creation of scientific knowledge initiates with a bold conjecture or a hypothesis. The conjectural statement of the scientist which is also considered as the personal theory of the scientist or hypothesis is presented initially in broad terms and is yet to be validated. 

     The initial broad conjecture proposed by the scientist is considered a Tier I hypothesis that is to be tested and validated empirically. This Tier I hypothesis is taken as an assumption and the scientist deductively reason and deduce logical consequences from it.

         The Tier-I hypothesis is a broad statement. To validate it or to test the validity of the statement,  the scientist deduce logical consequences from this broad statement that can be tested against the canons of empiricism. 

        To establish the veracity of the hypothesis, the scientist makes certain predictions from the hypothesis (Tier-I) through deductive reasoning. The deductions thus arrived at are also hypothetical and constitute the Tier-II hypothesis.

        The Tier-II hypothesis arrived at through deduction, is empirically verified. The confirmation of the Tier-II hypothesis validates the Tier-I hypothesis.

   Thus it is the verification of deductions arrived at from the hypothesis that a scientific theory is established, modified or dropped down. Thus Claude Bernard (1865) explicitly claimed that his methods involved two distinct phases viz. inventing a verifiable hypothesis and then testing the same.

       Thus the term deductive is justified in the name of the scientific method i.e HD Method.

If hypothesis and deductions are the key processes in the scientific method then why do we say scientific theory is empirically embedded?

    HDM involves a two-tier system of hypothesis (Trotta, et., al., 2013). A more general hypothesis is hierarchically created at a higher level to explain a certain set of observational data. At the second level in the hierarchy, there are one or more hypotheses that are deductively created as consequences considering the hypothesis at level one to be true. 

    The Tier-I hypothesis is validated through the validation of the Tier-II hypothesis. However, the Tier-II hypothesis is validated empirically. The deductively arrived consequences (or Tier-II hypothesis) are subjected to further observation and experimentation to verify them. 

       The necessity of empirical verification of the deduced consequences from the hypothesis makes scientific theories empirically embedded.  

What are the steps of the H-D Method?

               a. Hypothesising

Scientists faced with some explanation problem make a bold gesture and propose a hypothesis as a tentative explanation for some set of observational data. 

       b. Deduction

The hypothesis is taken as a true premise and following deductive reasoning, the scientist makes certain predictions. These predictions are logical consequences if the tier I hypothesis is taken to be true. The predictions are themselves hypothetical statements (Tier-II). The Tier-II hypothesis or the predictions or consequences emanating from the Tier-I hypothesis are more specific.

    c. Observation

The tier II hypothesis is empirically tested i.e. the consequences deduced need to be examined against the real-world processes. The observational data decides the fate of the tier I hypothesis- whether it is to be accepted as a theory, modified or discarded. 

The three-phase scientific method termed the hypothetico-deductive method (HDM) shows the hypothetical nature of SM. 

    The general pattern of reasoning goes like this:

Thomas Kuhn and Theory of Scientific Revolution:

Thomas Kuhn and Theory of Scientific Revolution:

Prologue

Every discipline is characterized by both stability as well as change. Stability in the discipline helps it to consolidate its theories and presuppositions whereas change brings in dynamism in the discipline and allows itself to enrich, expand and evolve. Philosophers of science are often concerned with the process by way of which change-termed as conceptual change by Toulmene, takes place in the discipline of science. There are different theories –that given by Collingwood, Thomas Kuhn and Toulmene. Thus the Structure of Scientific revolution by Thomas Kuhn is basically a theory of conceptual change in the discipline of science.

Dialogue

What are the key concepts included in Kuhn’s Theory?

To comprehend Kuhn’s theory, one need to be very clear about two key terms or concepts. The two key terms or concepts are

i. Paradigm

ii. Revolution

How can we interpret the term Paradigm?

According to Kuhn, during a given period of time, there exists a fundamental theory in science that is accepted by the community of scientists. The scientific community, accepts the theory and are engaged in further exploration, elaboration and consolidation of the theory. New applications are searched for the theory and the community, as a whole, adheres with the fundamental theory and its validity. Kuhn considered a paradigm as a way of thinking and acting that is accepted by the community of scientists who work under the guidance and standards of the existing paradigm.

Toulmene characterize Paradigm as a ‘set of presuppositions’ or a constellation of concepts along with a set of assumptions and procedures that together constitute a paradigm or a world view.

Is Paradigm permanent or it changes?

No changes do occur in paradigm and such change accounts for the conceptual change and development of the discipline of science.

Why and How do this change takes place?

Most of the time in the discipline of science, the community researches and explore answers to their questions under the guidance of the existing paradigm that they accept. This period is considered by Kuhn as the phase of Normal Science during which the scientists are able to explore new applications of the theory and the observations are satisfactorily explained by the paradigm.

However, certain observations emerge that could not be explained by the existing paradigm. Thus certain natural phenomenon could not be explained by the pre-Copernican theory. New theories emerges and many in the community affiliate with the new theories.  A sort of tension arises between different factions of scientific community adhering to the old and the new theory. The struggle between those who adhered with the Classical Physics and Relativistic physics is an example of such a tension.

This emerging tension eventually leads to a challenge to the fundamental assumptions and outlook of the existing paradigm. A sort of revolution takes place and the old paradigm gives way to a new paradigm.

What is scientific Revolution in Kuhn Theory?

According to Kuhn when the existing paradigm fails to explain several of the observations that arises during the normal phase, there arises a phase of crisis. Need is felt for a new theory that can explain the anomalies. When such a theory emerges, sort of tension arises between those who affiliate with the older theory and the new theory. Eventually, the new theory emerges full blown and it replaces the old one. A new world view with a new set of assumptions and outlook gets established and a new era of novel questions and researches arises. This change over was termed by Kuhn as a Scientific Revolution characterized by a shift in the paradigm.

For Kuhn, scientific revolution “are here taken to be those noncumulative developmental episodes in which an older paradigm is replaced in whole or part by an incompatible new one…”

What is the significance of Kuhn’s Theory?

Kuhn provided a new approach to view conceptual change in the discipline of science and hence explain the developmental process of the discipline. It also establishes the role of community of scientists in the conceptual change that occurs in science or for that matter in any other discipline.

Epilogue

Conceptual change is characteristic of any discipline including that of science. According to Kuhn, the conceptual change takes place through sort of revolution that Kuhn called as scientific revolution that leads to a change in paradigm that guides the research and inquiry in the discipline. A new theory emerges that replaces the older one and is able to explain the anomalies in observation that accumulated during the normal phase of science.