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Philosophy of Science

Philosophy of Science

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Philosophy of Science

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  1. Philosophy of Science Class 8

  2. Admin… • Teacher Evaluation • Pick up midterms • Outline/Topic Summary available at my office hours tomorrow

  3. Classic Tradition • The 1950’s and 1960’s marked the high point of what is commonly referred to as the ‘classical tradition’ in science. • What is this ‘classical tradition’? • It is a certain basic view of the world and of science which has been shared, to some extent by all of the philosophers of science we have considered so far.

  4. Assumptions of the Classical Tradition • There is an outside world, which exists independent from all observers. • The ultimate goal of science is an accurate (as possible) description of this observer independent world. • Scientists can observe the objective natural world, in some way, and learn about it. • the universe has underlying regularities that, if discovered can explain the behaviour of the universe.

  5. General Agreement that… • There is independent observation (if you had twenty scientists observing something, they would see it about the same). • Observation is not dependent on the particular observer, and deductive logic is not dependent on the observer. • Reality is also independent of any particular observer.

  6. Their important conclusion: Science is Objective!

  7. This is good because… It means we can use science to find out the truth about reality!

  8. A Requirement of Science? • The question is: • if you lose any of these assumptions, is it still possible to even do science? • In other words, can you be a scientist if you don’t believe in • An objective reality • A reality with causal universal laws • An objective observer (or collectively, a group of objective observers) who are able to draw objective conclusions from objective observations of reality.

  9. Two branches of Twentieth Century Philosophy of Science • Branch One: Logical Positivists, Popper • Branch Two: Duhem-Quine Thesis, Kuhn Branch Two- stayed focused on the issue of whether or not theoretical entities actually exist. (Both interested in truth of hypotheses)

  10. To say that a statement is true is to say that it accurately describes reality.

  11. Reality of Unobservable Entities • Suppose your theory has predictive power… • How could it have predictive power, if the entities didn’t actually exist? • The predictive power of theories provides independent objective proof of the reality of unobservable entities

  12. 16th-20th century: Adequate Justification • Scientific methods, scientific theories seemed to be working! • Science was progressing • Just before the start of the 20th century- it looked like science was on the verge of figuring everything out! • And then…

  13. Some problematic theories • General Theory of relativity • Quantum Electrodynamics • Heisenberg’s Uncertainty Principle

  14. Quantum Electrodynamics • The wave theory of light, the corpuscle theory of light  Science came up with very convincing evidence that stated that light travelled in waves.  It also became apparent, that evidence for the corpuscle theory of light could not be explained by the wave theory. • Eventually Einstein declared that , somehow, light behaved as both a wave and a particle.

  15. Conventionalism(Henri Poincaré (1854-1912), Pierre Duhem (1861-1916)) • The problem:  theoretical statements must be either supported or refuted with indirect tests.  indirect tests involve (theoretical) auxiliary assumptions.  In the face of contradictory evidence, the truth of a theoretical statement can always be saved by stating that some auxiliary assumption is false (a la Copernicus).  The only way to test the truth or falsity of auxiliary assumptions is through further indirect tests.  But the indirect testing of the auxiliary hypotheses will involve more auxiliary hypotheses, which will need to be tested... • This results in an infinite regress!

  16. Conventionalism(Soft Antirealism) • The Solution:  There is a great difference between statements made based on direct observation and statements whose truth is proved indirectly.  The truth of observational statements can be determined through observation.  However, if you try hard enough it is always possible to make any theoretical statement seem true • Therefore, theoretical statements can never be said to be either true or false.

  17. What kind of a solution is that!

  18. But wait, there’s more… • Science should still use theories! • Any number of theories can be found to help us manage our observation statements. • Theories must be consistent with our observations, and help us to make predictions. • We need not be concerned with their relation to reality. • Note: Conventionalism is not denying that there is a truth of the matter about reality.

  19. Conventionalism Tagline: Theoretical statements can never be declared as true or false. Theoretical statements are merely useful in helping us to organize (cope with) our observations.

  20. Conventionalism sounds great But it has put us on the path to trouble!

  21. Duhem-Quine Thesis(Strong Anti-Realism) • William Van Orman Quine (1908-2000) • However, he took it one step further.  Poincaré and Duhem had tried to protect observation statements from the Auxiliary Hypothesis infinite regress.  They said that observation statements could be declared true or false simply by observing them (direct testing) and so they were safe from the infinite regress that befell statements that relied on indirect testing. • Quine disagreed. He did not see a difference between theoretical and observational statements.

  22. Trusting Observations • Consider the simple observation: “my car is blue”. • How would you verify the truth or falsity of this statement?

  23. Theory of the World • In order to verify that the car is really blue, you must already have certain beliefs like: • “The true colour of this car is apparent to me when the sun is shining, because then the light rays correctly reflect and provide me with information about the colour of the car”. • These beliefs are part of a theory about the world. (Your own personal theory) • Theory? Oh no! Infinite regress!

  24. Important Detail! • Quine is not saying that the problem is that our senses are fallible. • Quine is saying: • All of our direct observations are necessarily connected to theory (through our network of beliefs) • All theory is vulnerable to the auxiliary hypothesis problem (as shown by Duhem and Poincaré) • Therefore- Even our direct observations are vulnerable to the auxiliary hypothesis problem.

  25. Strong Antirealism Tagline: There is no distinction between observation and theory. All statements are vulnerable to revision. (All statements are neither true nor false.)

  26. Realism Tagline: Scientific theories describe, to some approximation, the way nature really is. Unobservable entities really do exist.

  27. Starting to Challenge Objectivity • The antirealism philosophers: Picking at objectivity… • Classic tradition: scientists can become passive receptacles for what the world wishes to reveal. (methods of Bacon,Galileo) • The antirealists: It isn't that simple. We can't be passive observers of reality.

  28. Subjectivity • Reality would be said to be subjective if the nature of its existence depended on whether or not it was being observed and how it was being observed. • A person is said to be subjective when their observations or perceptions of reality are influenced by their own beliefs, desires or experiences. • For example, whether or not chocolate ice cream tastes good is a subjective matter. • Not necessarily bad…

  29. Bad for the Classical Scientists • According to the classical tradition: • Personal Subjectivity is bad for science! (Why?) • Scientists must be trained to be objective! • This is possible. (Bacon, Galileo) • Antirealists are starting to challenge the idea that this is possible… • But what is the alternative? No science?

  30. Thomas Kuhn (1922-1996) • The Structure of Scientific Revolutions (1962): • the assumptions of the classical tradition (including the presence of objectivity in science) are bad assumptions • science works perfectly well in the absence of total objectivity. Physicist, Historian, Philosopher

  31. Paradigms • According to Kuhn, every scientists approaches the world from within a particular framework of understanding. • Kuhn calls this framework a paradigm. • This framework shapes the way the scientist perceives the world, and determines, in part, how the world is perceived.

  32. The origin of personal paradigms • Fledgling scientists (i.e. those of you in this class who are doing science degrees) gain their framework by being exposed to examples of applications of the theories. • You learn about the meaning of existing scientific theories through exposure to these examples. • Newton’s theories (gravity? momentum?). The pendulum examples. • By seeing how Newton’s theories are applied to this situation, I learn about the meaning of Newton’s theories.

  33. Exemplars • In scientific community, at a given time, has certain standard examples of how a theory might be applied- i.e. the pendulum examples. • Kuhn called these standard examples exemplars. • By being exposed to these exemplars, students of science come to understand the meaning of a theory, and can then go on to use it in novel contexts.

  34. An Exemplar example • The idea of exemplars can be applied to more than just scientific theories. • Imagine that you want to learn the meaning of the word ‘bird’. • Someone might teach you the meaning of this word by taking you to the zoo and showing you sparrows, robins, ducks, ostriches and penguins, each time stating “That’s an example of a bird”. • Hopefully you will then be able to apply the word ‘bird’ correctly to new types of birds.

  35. The origin of paradigms • When science begins to investigate a certain aspect of nature, there are no paradigms or theories. • Very quickly however, individuals develop their own theories about the natural phenomenon. • Over time, these theories become more general and comprehensive- they become generic theories • Initially, there are a number of competing generic theories, but eventually one generic theory comes to be favoured by scientists. • This generic theory then becomes a paradigm, which will be passed on to new scientists in the area.

  36. The value of paradigms • They provide direction and motivation for scientists. (e.g. “I wonder what effect increased gravity has on pendulum behaviour?) • Furthermore, they allow scientists who share the same paradigm to effectively work together and communicate their findings in a consistent and comprehensible manner.

  37. Using Paradigms • Scientists will look for ‘facts’ relative to and try to solve puzzles relative to their paradigm. • Scientists will seek out observations that support their paradigms. • Scientists will try to clarify and expand the paradigm by developing precise laws, accurately measuring physical constants and applying their paradigm to new phenomena not yet specifically covered by the paradigm.

  38. Paradigm Example • Atomic Paradigm: • Everything is composed of small indivisible particles called atoms. • Different substances are composed of different types of atoms, or, sometimes, different combinations of types of atoms. • Phlogiston Paradigm: • Everything is composed of water, air, earth or fire, in some combination. (Phlogiston was the name given to the essence of fire). • Different combinations of these four substances lead matter to provoke different sensations in people.

  39. Applying the two different paradigms • look for ‘facts’ relative to and try to solve puzzles relative to their paradigm. Atoms vs..... Phlogiston… • Seek out observations that support their paradigms. Atoms vs........ Phlogiston • Try to clarify and expand the paradigm by developing precise laws, accurately measuring physical constants and applying their paradigm to new phenomena not yet specifically covered by the paradigm. Atoms vs..... Phlogiston

  40. Normal Science • A particular paradigm will provide scientists with both problems to solve and expectations of what solutions they will find. • Most of the time, this is how science progresses. (normal science). • However, occasionally, events arise that result in an overthrowing of the existing paradigm and its replacement with a new paradigm. • The new paradigm is often radically different and not compatible with the old paradigm.

  41. Scientific Anomalies • What causes the overthrowing of an existing paradigm? • Generally speaking paradigms are quite stable. If observations or results are not compatible with the paradigm they tend to be ignored or their relevance diminished in scientific circles. • Sometimes, however, an anomaly is so problematic that it can’t be ignored.

  42. Scientific Crisis! • Suppose a problem is too large for science to just ignore. • In this case, scientists might try modifying some parts of their existing paradigm (e.g. changing or adding auxiliary hypotheses). • Every effort will be made to hold onto the paradigm. • Eventually, however, too many of these anomalies may build up, precipitating a crisis in that area of science.

  43. Scientific Revolution • When a crisis occurs, a new paradigm is sought out to replace the existing paradigm. • Kuhn called the event where one paradigm was rejected and another found to replace it a scientific revolution.

  44. Incremental Progress • Generally speaking, the old paradigm and the new paradigm are not compatible. Facts in one do not translate into facts in the other. This runs contrary to the commonly held idea that, over time, science gradually increases its knowledge about the natural world. • Kuhn describes different paradigms as being incommensurable

  45. Differences between Paradigms • According to Kuhn, no aspect of the paradigms are spared this incommensurability. • Paradigms do not share: • Facts • Problems and solutions • Terms (even if they happen to have the same form, they do not share meaning) • Statements or subject matter

  46. Kuhn’s Strong Position • Can Kuhn really mean what he is saying here? • Wouldn’t measurements and basic observations (like “Smoke rose into the air”) still be consistent across paradigms?

  47. Paradigm- A world filter • According to Kuhn, a paradigm is like a filter that affects every aspect of the way we perceive the world. • To gain a better understanding of what this means, consider the following analogy- the helmet analogy: • All scientists wear special helmets, which transmit to them the sights, sounds, smells, of the real world. However, the helmet also acts as a filter and changes this sensory information when it is passed to the scientist.

  48. Different Paradigms, Different Worlds • For scientists whose helmets have the same filter, the world will appear the same. • For scientists who do not share the same filter, even simple observations will be experienced differently. • A paradigm is like one of these filtering helmets. It completely determines our perspective of the world. • Kuhn believes we need the filter provided by the paradigm in to have any understanding of the world.

  49. Kuhn the Relativist? • Kuhn does not think that different paradigms provide more or less accurate version of reality. • Returning to our analogy, it is not that some helmets have less of a filter than others. • Given this, does Kuhn think that any one paradigm is any better than any other paradigm? • This is similar to the question we discussed earlier about theories- how do you decide which theories are better than other theories?

  50. Kuhn Tries to avoid Relativism • Kuhn most emphatically does not wish to be considered a relativist. • He develops a number of criteria on which to compare paradigms. • Briefly, they are (Hung p.384): • Problem solving ability • Quantitative Precision • Predictive power (ability to make unexpected predictions) • Consistency • Simplicity • Aesthetics • Future Promise