Presentation on theme: "The Astronomer by Jan Vermeer. Models, Hypotheses and Theories Models, Hypotheses and Theories are essential to scientific reasoning. They are typically."— Presentation transcript:
The Astronomer by Jan Vermeer
Models, Hypotheses and Theories Models, Hypotheses and Theories are essential to scientific reasoning. They are typically arrived at via the inductive process of generalizing from observation. As such they are abstractions, concepts that aid us in the quest for knowledge.
Models Models are part of the theoretical structure of science. They do the work of providing a concrete picture of how our ideas correspond to an external reality. Models require imagination and the process sometimes defies logic, as when they come to scientists in dreams. Watson describes arriving at the structure of DNA by noticing spiral staircases. But the models must be tested against the world to see if the correspondence is faithful.
Types of Models Scale Models – a physical representation that is meant to be accurate but on a smaller or larger scale. For example, in the DNA model built by Watson and Crick, the model represented roughly one-billionth of an inch in the actual DNA molecule. Analog Models – a rough similarity between some physical reality one is attempting to represent and another well known reality. For example, the structure of the solar system is an analog model of the atom where electrons are roughly understood as analogous to planets. (This didn’t quite work out as the model was explored.)
Model of the Solar System
Model of the Atom Rutherford/Bohr Model
Cloud Model of the Atom Erwin Schrödinger’s Model
Double Helix Model of DNA
Model of the Synapse of a Neurotransmitter in the Brain
Theoretical Models and Theoretical Hypotheses Theoretical models are abstractions that can only be verbally described. As such they are part of an imagined world. Theoretical Hypotheses are result from asking whether the theoretical models imagined by scientists accurately represent the world. “A theoretical hypothesis, then, is a statement (claim, assertion, conjecture) about a relationship between a theoretical model and some aspect of the world.” (Giere, Understanding Scientific Reasoning, p. 25)
Hypotheses and Theories Hypotheses and theories are closely related. In the broad sense, they are interchangeable. In a more narrow sense, a hypothesis is a conjecture, an educated guess that has not yet been subjected to testing while a theory is a conjecture that has survived testing.
Hypotheses and Theories A scientific theory summarizes a hypothesis or group of hypotheses that have been supported with repeated testing. A theory is tentatively accepted as long as there is no evidence to disprove it. If evidence accumulates to support a hypothesis, then the hypothesis can become accepted as a good explanation of a phenomenon or a broad range of phenomena. A theory then is an accepted hypothesis.
Hypotheses and Theories Logically a hypothesis or theory is a consistent set of statements. It is possible that all the statements in the set are true, i.e., there are no contradictions.
Theories There is a sense in which our ordinary use of ‘theory’ and ‘opinion’ are interchangeable, as for example when one says ‘Well, that’s your theory,” or “I have a theory.” But in the sense in which the term is used in science, ‘theory’ is not simply interchangeable with ‘opinion.’ The equivocal use of ‘theory’ is a source of great confusion in arguments over science, (e.g., the theory of evolution).
Empirical and Theoretical Hypotheses Empirical hypotheses concern the production of some thing or occurrence of some event that can be observed. Theoretical hypotheses concern how something should be conceptualized. (Hurley, A Concise Introduction to Logic, p. 554)
Empirical and Theoretical Hypotheses Empirical hypotheses: When Neptune was finally sighted through a telescope, it was observed. When radium was obtained as a pure metal, it was finally observed rather than merely theorized. Theoretical hypotheses: When Newton conceptualized space and time as absolute, this was part of his theory of motion as the occupation of different places at different times.
Hypotheses and Theories Hypotheses and theories are also tested against reality. This process is generally accepted as deductive.
Scientific Theories According to Giere, a scientific theory has two components: (a) a family of models (b) a set of theoretical hypotheses Giere, Understanding Scientific Reasoning, p. 26.
Scientific Theories Good scientific theories, i.e., ones that are better than their predecessors, have: (a)Broader explanatory power, i.e., they explain more phenomena (b)Greater predictive power, i.e., they predict more phenomena (c)Unify more phenomena, and are therefore more simple. (d)Falsifiability, i.e., they have high empirical content and are therefore able to be proven false. (e)Fecundity, i.e., they lead to further extensions of the theory.
Grand Theories There are also theories within larger theories, e.g., terrestrial and celestial mechanics are parts of Newtonian theory, or Einstein’s theory of gravity is part of the General Theory of Relativity. Such grand theories are sometimes called ‘paradigms’ or ‘world-views.’ The most grand-scale theories today in physics are called ‘Grand Unified Theories’ (GUTs) or even the ultimate Holy Grail of Theories, ‘The Theory of Everything,’ (TOE), i.e., theories that attempt to unify all the diverse theories of physics into one grand theory— weak and strong nuclear forces, electromagnetism, and general relativity.
Hypotheses and Theories The logical positivists (R. Carnap, A. J. Ayer) thought of theories as made up of hypotheses, both of which could be analyzed in terms of their empirical and theoretical content. A hypothesis or theory is a belief about nature or reality, which is understood to be a network or system that can be broken down into separate statements. Their idea was to test theories for metaphysics, and eliminate any theoretical content that could not be verified.
Hypotheses and Theories Did the logical positivists “throw the baby out with the bathwater?” Is metaphysics (or the unverifiable theoretical content of scientific theories) necessary for any quest for scientific knowledge? Metaphysicians argue that without basic metaphysical concepts there would be no science.
Philosophical Considerations There are philosophical problems with some of the seemingly straightforward distinctions and issues raised above.
Doubts about Induction First, there are doubts about the role of induction in science. Is the process of arriving at models, hypotheses and theories really an inductive one? Some philosophers, such as K. Popper and C. Hempel doubt this and instead focus on the process of arriving at conjectures from problems.
Doubts about Induction Popper and Hempel think that it is a bit misleading to think that the scientific process begins with induction, because without a problem the scientist is blind about what is relevant. Only when one defines one’s problem and formulates the tentative hypothesis, they contend, does one begin the scientific process.
Doubts about Induction Did Crick and Watson construct their model of DNA by any kind of inductive process without a hypothesis in mind from the start? According to Giere, the problem was to discover the physical structure of DNA and they began to construct their model from what was already known about DNA in But… was the process before this inductive, i.,e., all the painstaking work in genetics and organic chemistry?
Can Theories be True? If truth is a matter or verification or confirmation, when do we ever get enough evidence to say that a scientific theory is true? What is required for verification? Inductive inference does not guarantee the truth of the conclusion, but rather only offers some probability that the conclusion might be true. So, no matter how many ravens we observe we can’t be certain that all ravens are black because there is always a chance that the next raven observed will not be black. All scientific laws and theories are currently accepted because they have held up in the past, but we don’t know if they will continue to hold in the future. In what sense then can science give us knowledge about the world, i.e., justified true beliefs in Plato’s sense?
Can Theories be True? The idea that a model, hypothesis or theory is true if it fits the world presupposes a concept of truth (difficult in itself) and more specifically a correspondence theory of truth that by no means is universally accepted by philosophers. (Giere, Understanding Scientific Reasoning, p. 25) The very idea of a statement or belief corresponding with an external reality has many problems, and so some philosophers defend other theories of truth (coherence theory, pragmatic theory).
Discovery or Creation? Does science discover or create reality? Or both? When Crick and Watson constructed the model for DNA, did they create or discover reality? When Ptolemy, Copernicus and Kepler created models for the solar system, did they create or discover reality? When neuroscientists construct models of neurotransmitters, do they create or discover reality?
Discovery or Creation? Some philosophers, realists, think that there is sense to the idea of mapping onto reality and getting approximations to truth. The concept of verisimilitude contends that our scientific theories have a nearness to truth or the way things are. As such, the realists (Karl Popper, W. V. Quine) think that our abstractions are human creations but aid in the discovery of the way things are.
Discovery or Creation? Others, social constructivists, contend that the abstractions are just constructions, products of culture and are doubtful about the sense in which these can be called ‘true.’ Models, hypotheses and theories are human creations, and as such remain constructions like any other human creations. They are useful fictions. Social constructionism is part of the postmodern movement, created by Karin Knorr- Cetina, Bruno Latour, Barry Barnes, Steve Woolgar.
Discovery or Creation? ‘Reality’ is a value concept rather than an ontological one. The numerous realities so formed comprise, according to this view, the imagined worlds of human social existence and activity, gradually crystallized by habit into institutions propped up by language conventions, given ongoing legitimacy by mythology, religion and philosophy, maintained by socialization, and subjectively internalized by upbringing and education to become part of the identity of social citizens.
Theoretical and Empirical Hypotheses Is the theory of evolution a theoretical or an empirical hypothesis? Biologist Richard Dawkins says it is a theory that has been confirmed and therefore is fact. If Dawkins is right then, the theory of evolution is an empirical hypothesis.
Theoretical and Empirical Hypotheses Others doubt that any theory of this sort, or any sort, can be confirmed. (Popper, Hempel and Quine, for example) It is rather tentatively accepted as the best we have, nothing more, nothing less.
Theoretical and Empirical Hypotheses W. V. Quine liked to quote the positivist, Otto Neurath, who compared science to the busy sailor who must rebuild every part of his ship while staying afloat. There is no solid foundation of science, that is, a foundation in truth. Science is rather an on-going process of attempting to discover the way the world is under the guidance of fallible and corrigible but useful theories, theories that will all be proved false sooner or later.
Theoretical and Empirical Hypotheses The problem with the distinction between empirical and theoretical hypotheses is that observation is theory-dependent or theory- laden. For example, any observation a sunrise will be interpreted through some construct. The question: “Does the sun move or not?” will depend will depend entirely on the theory. So, as the point goes, all science is like this. What one sees is dependent upon what one is conditioned to see via the theory.