Daniel Hoyt
Dr. Ess
Philosophy of Science
May 4, 2000
A Referat
Experimentation and Scientific Realism
By
Ian Hacking
"One of the most lively and persistent debates in twentieth- century philosophy of science is that between empiricists and realists concerning the status of scientific theories. Are scientific theories to be understood as offering (or at least intending to offer) a true account of the world? And if we accept scientific theories as true, should we believe that the entities they appear to postulate really exist?"
-- Theodore Schick, Jr.
A. Realism/ Anti-Realism debates on the level of theories are necessarily inconclusive:
1. The realism of a theory is not readily provable because it deals with a proposition about the future.
2. Theories are interpretive. That is, they are able to be taken from different experiments and ideas and accepted and rejected based on opinion and argument. This allows socially- formed knowledge to affect the validity of a theory (430).
Conclusion: Realism should not be applied to scientific theories. A majority of debates concerning the place for realism have only talked about theories. So, what should we argue about?
B. Realism of entities is the only acceptable form
1. Proving the existence of an entity is problematic. We want to show that something exists, so we come up with experiments to prove it is really there, even though it is not directly observable.
2. Only when we manipulate an entity are we actually able to prove its existence.
3. Realism applies to entities because no amount of faith or optimism must be used. We know the entity exists now, not in some theoretical future. For this reason, the "presence" of entities makes them a candidate for true scientific realism (428).
"The experimentalist need only be a realist about entities used as tools (428)."
"Experimenting on an entity does not commit you to believing that it exists. Only manipulating an entity, in order to experiment of something else, need do that (429)."
C. The understanding and definition of an entity is not necessarily static.
1. "Electron" was understood in varying degrees, with differing theories and calculations, but it always referred to the same basic thing (430).
2. Putnam explains that meaning is a vector of various concepts, with the actual referent only being a part of the definition. Thus, although how we understand an entity might change and be revised, the entity itself is not changed or less real because we do not wholly understand it.
3. Scientists usually form in groups of those who share the same ideas, support the same theories, etc. The places they were taught, the teachers they had, even the textbooks they used could each instill a slightly different view on many different issues (430). This helps Hacking dodge any grouping of his work with the Social Constructivists. He sees how sociological tendencies can lead to corrupt scientific theories, but this is the limit of the corruption. Entities and their realism is another situation completely.
"Serious discussion of inferred entities need no longer lock us into pseudo- problems of incommensurability and theory change (431)."
"Naturally, teams tend to be formed from like- minded people at the same institute, so there is usually some real shared theoretical basis for their work. That is a sociological fact, not a foundation for scientific realism (430)."
D. Experimentation: Twisting the Lion's Tail
1. Experimentation is using something understood in nature to prove something that is not (431).
2. Entities can be viewed as Iying on a continuum: some are very well understood, while others are vaguely comprehended. Still others are merely guessed at, with no concrete surety of their existence.
3. The more "real" entities can be used to interfere with nature in order to get a grip on the less understood.
4. Reality of the unobservable entity (432)
a. We view observable entities as real because we can do with them, what we can do to them, and what they can do to us.
b. Unobservable entities can be manipulated in the same way. That is, we can interfere with nature by using unobservable entities to get observable results.
c. Conclusion: The same logic that makes macroscopic entities "real" must also make microscopic entities "real" as well.
d. Example: not only do microscopes help us to look at Extremely small objects. We validate the specimens seen under a microscope because the microscope allows us to see what we are doing to it. The simple viewing of something is only a small part of making it "real." The microscope helps us see the other ways that we are interfering and manipulating that object (432).
E. The experimental argument for realism
1. Some entities are regarded as real, while others are still considered theoretical—what is the difference?
2. Instruments are used that employ electrons (again, Hacking's example)
3. Electrons must be tacitly seen as real before we decide to manipulate them in order to understand other entities.
4. Here, Hacking's exhaustive defense of entity realism moves directly into an explanation of how apparatus are used in experiments, and how these entities can be viewed as real even if we do not understand every detail of their existence.
"We are completely convinced of the reality of electrons when we regularly set to build - and often enough succeed in building - new kinds of devices that use various well understood causal properties of electrons to interfere in other more hypothetical parts of nature (433)."
F. The Example: Parity and weak neutral currents
1. Nature has four forces:
a. Gravity
b. Electromagnetism
c. Strong forces
d. Weak forces
2. Where strong forces are 100 times stronger than electromagnetism, they only work in distances roughly equal to the diameter of a proton. Weak forces are 1/ 10,000 times as strong as electromagnetism, but act over a distance over 100 times as large strong forces. Also, Strong forces act only on hadrons (protons, neutrons), while weak forces work on hadrons and leptons, which include electrons.
3. Theoretical particles called bosons carry these weak forces over a given distance. These forces can be charged (+ or -). In the 1970's there appeared assertions about the existence of neutral weak currents. So, there must be positive, negative, and neutral bosons to carry these forces.
4. Parity is the direction of the spin- vector of an electron in relation to the direction it is traveling in a beam. Particles have either right handed or left- handed polarization. muon neutrino break this theory apart by possessing only left- handed polarization
6. This parity violation was found in weak charged currents .... so what about weak neutral currents? This was the background of a new experiment.
7. PEGGY II
a. LASER beam is used to produce a beam of light. The light is sent through two different instruments, which make it circularly polarized light.
b. This circularly polarized light is sent at a crystalline substance called gallium arsenide.
c. When the light hits the crystal, it emits a large number of linearly polarized electrons
8. Here, Hacking goes into detail about the kind of bugs that can interfere with the above experiment. The bugs can range from problems with the statistical interpretation of the data, to dust on the crystal leading to systematic errors in the data. He is hoping to show us just how many minutiae need to be accounted for when an experiment is run. These small bugs can each significantly change the outcome of the experiment. Because of problems like these, it is easy to see why many experts disagree with theories that are supported by experiments.
9. Although we may disagree with the outcomes of an experiment like this one (which happens to deal with bosons), few scientists, if any, would disagree with the electrons that are used as tools in this experiment. Not only is the existence of said electrons hardly contestable, the very traits of electrons that we are manipulating then calculating are rarely seen as arguable. This is a tacit consent to the existence and traits of electrons from many different experts in the sciences.
"Once upon a time, the best reason for thinking that there are electrons might have been success in explanation. Lorentz explained the Faraday effect with his electron theory. But the ability to explain carries little warrant of truth (436)." Once again, Hacking argues that it is not simply talking about an entity or postulating that it exists that makes it real. Only in our ability to understand how to use that entity on something else (by employing properties that we know and understand about it) can we circuitously prove that it is "real."
G. The Philosophical background on real entities
1. Atomism has been the classical subject of realism/ Anti- realism debates
2. [Early] Positivism has pushed us even further away from seeing entities as real in nature (438).
"Some hypotheses consist of assumptions as to the minute structure and operation of bodies. From the nature of the case of these assumptions can never be proved by direct means. Their merit is their suitability to express phenomena. They are Representative Fictions." - Alexander Bain (1870)
3. Assertions on the structure of particles and matter must be seen as intellectual tools, but not real entities that actually exist in nature.
4. Anti- realism about entities made sense when we did not have the knowledge or tools to be able to test for their existence. We have the ability to do such things now, but the anti- realist ideals are permanently ingrained in our minds.
5. This relates to 17th century epistemological problem: Knowledge, even if it is a correct representation, can never be objectively tested because we can never get outside of the world in order to determine knowledge's validity. We are never free to act like spectators to the world of knowledge, so we can never prove it (438).
"To attempt to argue to scientific realism at the level of the theory, testing, explanation, predictive success, convergences of theories, and so forth is to be locked in a world of representations. No wonder that scientific antirealism is so permanently in the race. It is a variant on 'the spectator theory of knowledge' (438)."
6. Hacking's disclaimer: "Manipulatability" is not the only means of bringing an entity into definite existence. Here, Hacking seems to be dodging the Social Constructivist attacks by telling us that we must not assume that entities exist only when we use them as tools. Instead, we can only be totally sure for ourselves that they exist in these cases (438).
Along these same lines: Many entities can be seen as real for long periods of time. But, unless they cross the threshold from theories on existence into explaining entities, they cannot be seen as real.
"A skeptic such as myself has a slender induction: Long-lived theoretical entities which do not end up being manipulated commonly turn out to have been wonderful mistakes (439)."
Conclusion: Hacking's arguments are very exhaustive. He hopes that using huge examples and historical cases will help him make his case. He seems to be walking a tightrope between to very opposite epistemologies: On the one hand, he seems to hint at a traditional masculine ideal that objects are not meaningful unless we can do something with them. That is, manipulation is the ultimate goal of science, and the true measure of our understanding of something is how we can control it. This view is opposed by a feminist critique that science should be seeking to understand, not necessarily control the natural world. Hacking walks a fine line between these two thoughts.