Consider what we will call the “positivistic view of science”
Definition 1 (postivistic view of science) Science consists of the following key features:
Kuhn views this picture of science as problematic. Kuhn starts The Structure of Scientific Revolutions (hereafter SSR) by claiming that history can effect a profound transformation in how we view science. According to Kuhn, the historian of science has two main tasks:
Concerning the second of the two tasks, Kuhn notes that (i) historians have struggled with giving an account of what part of earlier theories was “myth” and what was “scientific” and (ii) this renders problematic our view of science as accumulative. Consider a theory (call it “theory X”) that was once accepted as scientific knowledge but is later replaced by a newer theory (call it “theory Y”). Concerning theory X, the historian faces a dilemma.
Definition 2 (Historian’s Dilemma) If theory X is a myth (non-science), then this myth was produced by the same general method and accepted by the same general reasons that produces scientific knowledge. If theory X is scientific knowledge, then X and not-X are both true.
There are three possible responses to the dilemma if it is genuine.
Discussion 1 What is the correct answer to the historian’s dilemma to science?
Let’s assume, temporarily, that (3) is the correct route. If this is the case, then we need a different picture of how science has proceeded through history. Thomas Kuhn provides such an image. In contrast to an image of science that is the result of gradually accumulating knowledge through the use of an objective, unquestioned, value-free method, Kuhn provides the image of science as one marked by radical disruptions (revolutions) and making use of an often arbitrary, value-laden method.
Before delving into the details of Kuhn’s account, it is helpful to (i) obtain a general picture of how Kuhn sees the development of science and (ii) get clear on some of the key terms.
Note 1 (Science begins as pre-science.) According to Kuhn, the story of how science progresses begins with prescience. “Prescience”, in short, is characterized by there being no consensus about the general nature of some scientific phenomenon and debate about the fundamentals of science.1 In particular, “pre-science” has the following features:
Note 2 (Pre-science evolves to normal science when individuals adopt a scientific paradigm.)
The transition from pre-science to normal science occurs when individuals become committed to what is known as a “paradigm”. 3
Definition 3 (paradigm) A set of general theoretical assumptions, laws, methods, techniques that are adopted by a community of individuals, but also:
In short, a paradigm gives us a particular model of scientific activity that is usually marked by some significant scientific discovery or theory. This model of scientific activity has two characteristics:
Example 1 (History of Light)
In each case, scientific practitioners are said to accept a paradigm. They accept certain fundamental assumptions about the nature of light and then proceed to investigate more esoteric, specific, highly-specialized problems relating to light. What they do not do is question its fundamental nature, viz., what light is.
In short, pre-science begins as a chaotic group of theories where there is little consensus about what a certain scientific phenomenon is. Each individual creatively tries to address what that phenomena is, how to investigate it, and various other issues from the ground up. This leaves us with a chaotic and diverse array of theories that are largely at odds with each other.
With the acceptance of a scientific paradigm, normal science begins. In normal science, there is a consensus about what light (or some other phenomenon) is, and this information is codified in textbooks, scientific journals, and societies. Scientists turn from fundamental questions to highly esoteric questions about that phenomena and attempt to answer these questions within the terms of the paradigm.
Note 3 (Once a paradigm is accepted, normal science is now practiced.) Once individuals accept a paradigm, these individuals are practicing “normal science”. Kuhn notes that “normal science” is the kind of activity that scientists do most of the time, that it involves certain shared assumptions about the fundamental entities that compose the world (and how they relate), what kinds of questions can be legitimately asked, and what are legitimate answers to these questions. For the most part, practitioners of normal science attempt to resist novelty. It is only when there is some problem (anomalies) that cannot be legitimately answered by the accepted methods and solutions that scientists will allow a hearing for more creative solutions.
Definition 4 (Normal science) Normal science is “research firmly based upon one or more past scientific achievements, achievements that some particular scientific community acknowledges for a time as supplying the foundation for its further practice” (SSR:10).
Note 4 Normal science then is:
Note 5 (When falsifying phenomena build up in normal science, there is a crisis.) Various falsifying observations or phenomena are observed, these build up to a point that individuals begin to question the paradigm. Normal science evolves into a state of crisis.
Definition 5 (Crisis) A crisis is a state of science where serious anomalies threaten the current paradigm.
Definition 6 (anomaly) An anomaly is any problem with a paradigm.
The presence of an anomaly becomes serious to a paradigm when
When a paradigm falls into crisis, creative solutions emerge. These new solutions, in effect, challenge the fundamental assumptions of the old paradigm, and, in effect, propose new paradigms. When a new paradigm is accepted and the old paradigm rejected, a revolution has occurred. “The extraordinary episodes in which that shift of professional commitments occurs”, Kuhn writes, “are the ones known in this essay as scientific revolutions” (SSR:6).
Some revolutions include:
The most radical part of Kuhn’s theory is the following:
What argument does Kuhn have for these two claims? The short and sweet of Kuhn’s response is this: when a revolution occurs, and the scientific community replaces its current paradigm with a new paradigm, the new and the old paradigms are not comparable. They are incommensurable.
What does it mean for two paradigms to be incommensurable and why would this imply that science is not progressive and theory change is not objective?
Definition 7 (incommensurability) X is incommensurable with Y if and only if X cannot be compared with Y in terms of whether X is better than Y.
If two paradigms are incommensurable, they cannot be compared. And, if they cannot be compared, one cannot be said to be better or worse than the other. And, if one cannot be said to be better or worse than the other, then this seems to imply that the choice to abandon one paradigm for another is not guided by any feature of the new paradigm that makes it any better.
In what ways are scientific paradigms incommensurable? There are two ways that two paradigms and can be said to be incommensurable.
The first is what we can call linguistic incommensurability. This type of incommensurability can be thought of in two different ways:
In short, if two paradigms are linguistically incommensurable, the claim is that they cannot be compared. And, if they cannot be compared, one cannot be said to be better or worse than the other. And, if one cannot be said to be better or worse than the other, then this seems to imply that the choice to abandon one paradigm for another is not guided by any feature of the new paradigm that makes it any better or worse.
Objection 1 (Incommensurability and Incompatibility.)
The problem with this notion of incommensurability is that it seems as though it makes it impossible to talk about differences between paradigms at all.
The way that Kuhn sets up the shift from one paradigm to the next seems to imply that the different paradigms are incompatible. That is, we shift from one paradigm that makes certain claims about the fundamentals of the universe (or some phenomena) or about laws to another. The problem though is that if two paradigms are incommensurable then they cannot also be incompatible.
If two paradigms are incompatible, then they both cannot be true at the same time. So, if X and Y are incompatible: if X is true than Y is false and if Y is true, than X is false. But, if X and Y are incommensurable, X cannot be compared with Y, and so we cannot say that X and Y are incompatible.
But this is absurd since we think that paradigms (scientific theories) do conflict with each other.
This brings us to the second kind of incommensurability, what we can call evaluative incommensurability. On this incommensurability, and make use of different standards for evaluating what counts as a good theory, argument, or explanation. That is, if only a paradigm sets the standards of evaluation for what counts as a good theory, then each paradigm will count its own theory and arguments as successful, while it will count all others as unsuccessful. That is, if meets the standards of but not , then will count as a good theory while will count it as a bad theory. Similarly, if meets the standards of but not , it will be counted as good theory by but not .
We can imagine simple examples where a paradigm sets the standard for what constitutes a good explanation by requiring that we take into account certain entities and relations that another paradigm might not allow, e.g. an explanation only counts as good iff it can take into account of how it fits with God’s goodness.
Example 2 (Causal/mechanical or mathematical/formal explanation) We can imagine two different paradigms. The first requiring a causal/mechanical explanation for certain phenomena while the other requiring a mathematical/formal explanation.
For example, Newton’s theory of gravity states that “The gravitational attraction force between two point masses is directly proportional to the product of their masses and inversely proportional to the square of their separation distance. The force is always attractive and acts along the line joining them.”
Note that this explanation of gravity is purely a mathematical / formal explanation and does not state what causes gravity. That is, it does not state the mechanism that causes two masses to attract. If a paradigm says that purely mathematical explanations are sufficient, then Newton’s theory is a good theory. If it says that it is necessary to explain what causes gravitation attraction, then this theory would be problematic.
This particular line of argument assumes that there is no paradigm-neutral (theory-neutral) data, information, evidence that we can appeal to that would allow us to say that one paradigm is better than another paradigm. And, to some extent, there is good reason to believe this given the following:
In short, given that each paradigm judges what is and isn’t a good argument and there not being any theory-neutral (paradigm-neutral) evidence to decide between different paradigms, it looks like there is no way of determining which paradigm is better or giving any account of scientific progress.
Objection 2 (Kuhn’s theory makes scientific knowledge relative to a paradigm.) If what makes a theory successful is set by the paradigm, then a theory’s success is relative to the paradigm from which it is evaluated. Theories are not getting better and better as we transition from one theory to the next (since each paradigm evaluates its theory as sufficient and others as insufficient), but are being evaluated by different paradigms. In short, there is no measure of evaluation for evaluating paradigms.
This is counter-intuitive because: