Should we trust Science? (1900s)
The claim that we can be certain of scientific knowledge was disputed by Scottish philosopher David Hume's argument that there is no necessary truth to the idea that the future will resemble the past. In 1748, Hume argued that concepts like cause and effect are acquired by habit and, given our limited experience, we can never be certain that our experiences are objective. We may assume that all swans are white, for example, if we have only ever seen white swans, yet no amount of observations can disprove the idea that black swans exist. People who have only ever seen black swans could equally conclude that white swans do not exist. This is known as the problem of induction.
In 1934, Austrian-British philosopher Karl Popper argued that science can overcome the problem of induction with falsification (Popper, 2002). Popper argued that science can be distinguished from pseudo-science because all scientific theories can be proven false. There is no reason to abandon a theory until it is falsified, however you can never be certain that any theory is correct. Science also makes novel predictions, these are not used in the construction of the theory and correctly predict aspects of a phenomena we are not already aware of.
The philosophy of science distinguishes between metaphysics and epistemology. Metaphysics is concerned with what is objectively true and epistemology is concerned with what we can know. Scientific realism is a branch of epistemology which claims that it is rational to believe science provides true knowledge about the world. Scientific antirealists claim that it is only rational to believe in certain aspects of science, usually those that we can verify with our own eyes.
Scientific realists state that the aim of science is to seek the truth and that the claims of science tend to be based on truth. The most persuasive argument for scientific realism was developed by British-Australian philosopher Jack Smart in 1963 (Smart, 2008) and extended by American philosopher Hilary Putnam in 1975 (Putnam, 1979), this is known as the no miracles argument. The no miracles argument states that we should infer that scientific theories are true because, historically, science has been incredibly successful. Canadian philosopher James Robert Brown defined the success of science in three ways; firstly, science organises and unifies a great variety of known phenomena. Secondly, our ability to do this is more extensive now than in the past and thirdly, science is statistically more successful at making novel predictions than it would be if we were just guessing (Brown, pp.3-26).
Scientific realists argue that it is not surprising novel predictions are successful, it is what we would expect if the theory were true. If it were not true then it would be very unlikely, miraculous even, if consequences of the theory were right. Putnam claimed that "realism is the only philosophy that does not make the success of science a miracle" (Putnam, 1979, pp.73). Smart argued that it would be a "cosmic coincidence" if the theoretical entities suggested by physics were not real.
The no miracles argument relies on the fact that truth is the best explanation for success because it is the simplest explanation, this type of argument is known as inference to the best explanation. Scientific antirealists argue that we do not have enough evidence to support this claim and so do not accept the no miracles argument. One problem with inference to the best explanation is that there is no accepted definition of simplicity. Any amount of complexity is accepted in a theory, as long as it is simpler than its competitor and the discovery of extra complexity will not necessary lead us to abandon it.
The most persuasive argument for scientific antirealism was suggested by American philosopher Larry Laudan in 1981, this is known as pessimistic meta induction (Laudan, pp.19-49). Laudan argued that we do not have a good enough reason to believe in the existence of theoretical entities, objects which we cannot see with our own eyes, because history is full of examples of scientific theories that were later shown to be false. Newtonian physics was certainly successful, for example, yet Newton made assumptions that are inconsistent with Einstein's theory of general relativity. This would mean that Newton's theory is now considered wrong and so we should infer that relativity is probably wrong too. In fact, all of our current scientific theories are probably wrong.
Both approaches are persuasive, the ability to use a computer, for example, would appear to be a miracle if science does not provide a correct explanation for how it works. Yet it would be wrong to claim that science has reached a full understanding of the world and it is true that science progresses by abandoning past theories, even ones that have been accepted for hundreds of years. A good explanation for scientific realism should take this into account.
In 1984, American philosopher Richard Boyd argued that scientific theories are rarely abandoned entirely, succeeding theories usually contain aspects of their predecessors (Boyd and Leplin, pp.41-42). In 1905, French philosopher Henri Poincare had suggested that the structure of theories carries over as limiting cases in succeeding theories (Poincare, pp.162). The equations remain true because they preserve some aspect of reality and this explains why a false theory can make successful novel predictions. Newton's theory is a limiting case of Einstein's and if we accept that this is how theories have progressed in the past then we have a good reason to believe that they will continue to do so in the future. One problem with this explanation is that it claims it would be a miracle if a successful theory was overthrown without being referenced in by its successor, this is because it would be miraculous if science was successful without containing an aspect of truth.
Scientific antirealists argue that the success of science can be explained without assuming science refers to the truth. In 1983, American philosopher Nancy Cartwright suggested that the predictive success of science is an accident that arises from what Irish philosopher George Berkeley called the 'compensation of errors' (Cartwright, pp.140). This means that adjustments are made until the correct observational effects are predicted, one incorrect adjustment can be corrected by another. In 1980, American philosopher Bas van Fraassen argued that scientific theories are not successful because they are true but because theories that do not make correct observational predictions are dropped, in the same way that natural selection drops species that do not positively adapt to their environment (van Fraassen, pp.1064-1087). Both of these approaches fail to explain how science is so successful at making novel predictions. Brown claimed that this problem is analogous to a radical change in the environment for species and so the metaphor breaks down as they would not necessarily survive this (Brown, pp.7).
van Fraassen argued that we still do not have good enough reasons to believe in the existence of entities that cannot be verified by direct observation with the naked eye because there are an infinite amount of theories which give rise to the same observational results. This can be highlighted with the example of curve fitting. There are an infinite amount of lines that can be drawn on a graph and so scientists must make inferences beyond the data. They must assume that the simplest approach is correct. van Fraassen argued that scientists are not justified in this claim, theories should only be described as empirically adequate, referring to the fact that they can successfully explain our observations (van Fraassen, pp.1069). There is no way to know which, of an infinite amount of empirically adequate theories, are correct.
van Fraassen's argument draws an absolute distinction between observable and theoretical entities yet we do not accept this distinctive cut off point in real life. This problem was highlighted by American philosopher Grover Maxwell in 1962 (Maxwell, pp.1052-1063). Maxwell argued that the continuous transition between what we see through, "ordinary spectacles…an ordinary window pane" and "temperature gradients" through to the use of instruments such as telescopes and microscopes, shows that the distinction between observable and theoretical entities is vague and arbitrary. Maxwell argued that because there is no logical connection between observation and existence, there is no reason to believe that unobservable things do not exist.
van Fraassen accepted Maxwell's claim that the boundary between observable and theoretical entities is vague, but argued that this is not important as there are many cases where a clear distinction can be found. There is a vast difference, for example, between the electron microscope - microscopes which use electrons, instead of light, to illuminate - and the naked eye.
In 1985, New Zealand philosopher Alan Musgrave argued that van Fraassen's boundary does not make sense since some people can see more with their naked eyes than others (Musgrave, pp.1095). Sight is something which varies from person to person and is dependent upon our evolutionary history. In 2001, British philosopher Philip Kitcher suggested that we can prove instruments like glasses and telescopes work because those with better vision can verify what is seen by others (Kitcher, pp.151-197).
By 1981, Canadian philosopher Ian Hacking had shown that this approach also applies to microscopes (Hacking, 1985, pp.132-152). This is evident when we resolve details of macroscopic objects, observe macroscopic objects at the same time as microscopic objects or observe a reaction after interfering with a microscopic object. Hacking argued that this continuity can even be shown using instruments that depend upon the existence of theoretical entities in order to work, such as electron microscopes. Van Fraassen claimed that these arguments are irrelevant, we simply need a stronger reason to believe in entities which we cannot verify with our own eyes (van Fraassen, pp.1075).
The Star Garden
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Images from electron microscopes; Pollen from a sunflower, Pollen from an oriental lily, Pyralidae moth
In 1982, Hacking argued that theoretical entities can be proven to exist without the need for theory or observation, this is because we can use them as tools to successfully build instruments. Hacking argued that we are, for example, "completely convinced of the reality of electrons when we regularly set out to build - and often enough succeed in building - new kinds of device that use various well understood causal properties of electrons to interfere in other more hypothetical parts of nature" (Hacking, 1982, pp.1158). Hacking claimed that many experimental physicists are in fact realists about entities rather than theories.
The first objection to Hacking's entity realism is that his definition is not wide enough to allow for realism in astrophysics since astronomical objects cannot be used to build instruments. In 1993, American philosopher Dudley Shapere argued that this problem can be avoided by extending Hacking's argument to allow for more passive forms of interference.
The second objection was raised by American philosopher David Resnik in 1994 (Resnik, pp.1176 and pp.1180). Resnik argued that Hacking's entity realism fails because Hacking must rely on some kind of theory in order to interpret that instrumental results are successful. This problem may be resolved by combining Hacking's entity realism with Poincare's argument that the structure of theories carries over as limiting cases in succeeding theories, however it then faces the same problems as Poincare's theory.
Images from electron microscopes; Snowflake, Blood, Spider and silk
References
Boyd, R. and Leplin, J., 1984, 'The Current Status of Scientific Realism', Scientific realism, Leplin, J. (ed.), University of California Press, California, pp.41-82
Brown, J.R., 1994, 'Explaining the success of science', Smoke and mirrors: how science reflects reality, Routledge, Oxford
Cartwright, N., 1983, 'How the laws of Physics lie', Oxford University Press, Oxford
Hacking, I., 1982, 'Experimentation and Scientific Realism', Philosophy of Science; The Central Issues, Curd, M. and Cover, J.A. (eds.), Norton & Co., New York, pp.1153-1168
Hacking, I. 1985, 'Do We See Through a Microscope?', Images of Science, Churchland, P. and Hooker, C. (eds.), The University of Chicago Press, Chicago
Kitcher, P., 2001, 'Real Realism: The Galilean Strategy', The Philosophical Review, Vol.110
Laudan, L., 1981, 'A Confutation of Convergent Realism', Philosophy of Science, Vol.48
Maxwell, G., 1998, 'The Ontological Status of Theoretical Entities', Philosophy of Science; The Central Issues, Curd, M. and Cover, J.A. (eds.), Norton & Co., New York
Musgrave, A., 1998, 'Realism verses Constructive Empiricism', Philosophy of Science; The Central Issues, Curd, M. and Cover, J.A. (eds.), Norton & Co., New York, pp.1088-1114
Poincare, H., 1952, 'Science and Hypothesis', Dover, New York
Popper, K.R., 2002, 'Conjectures and refutations: the growth of scientific knowledge', Routledge, London
Putnam, H., 1979, 'Philosophical Papers: Mathematics, Matter and Method', Vol.1, Cambridge University Press, Cambridge
Resnik, D., 1994, 'Hacking's Experimental Realism', Philosophy of Science; The Central Issues, Curd, M. and Cover, J.A. (eds.), Norton & Co., New York, pp.1169-1185
Smart, J., 2008, 'Philosophy and Scientific Realism', Routledge, Oxford
van Fraassen, B., 1998, 'Arguments concerning Scientific Realism', Philosophy of Science; The Central Issues, Curd, M. and Cover, J.A. (eds.), Norton & Co., New York