Ladyman Chapter 1-2 UC 2002 Fall Veni, Vidi, Induxi Louis, Jessica, Sandra, Floris Sci101 History & Philosophy of Science
Order of Appearance • Sandra (Background Information) • Jessica & Louis (Discussion) • Floris (Gruesome Theories) • Louis & Jessica (Discussion)
Background Information Sandra
Scientific revolution • Aristotle • deduction • Bacon • induction
Deduction All M are P S is M S is P
Induction M1, M2, M3, Mn are P All M are P
Hume • Addressed problems of induction • Cause and effect
Discussion Jessica & Louis
Hume says: In each case, the moral is that a priori reasoning and argument gets us nowhere: "it is only experience which teaches us the nature and bounds of cause and effect, and enables us to infer the existence of one object from that of another.”
Gruesome Theories The role of theories in inductive science. Floris
Topic Outline • What are scientific theories? • Characteristics, Inner Mechanics • What can go wrong? • The role of theories in inductive reasoning. • The ‘Grue’-paradox
Brainstorm • Once again; brainstorm about ‘Theory’
Theory Characteristics I • A theory tries to explain why certain events take place. • Example: “I (Ptolemy) designed my theory about the solar system to explain the observed movement of the planets and stars.”
Theory Characteristics II • How do they go about explaining? • Compare: • ‘This here is a chair.’ (hardly a theory) • ‘There is a force on this chair.’ • Can we directly see a force? • Only its results. • Scientific Theories postulate things that cannot be directly perceived.
Likewise, • Likewise, a generalised rule cannot be perceived. • Causal relation: • ‘If I drop this chair out of the window, it will fall to the ground.’ • We cannot directly ‘see’ this rule in nature; it rather is a pronunciation of our notion of regularity in accumulated perceptions of objects falling when dropped.
Results • Since we cannot directly perceive what a theory postulates, therefore, in order to verify the theory, we can only look at the perceivable predictions it makes. Observations Generalised Rules Theoretical X1 X2 X3 X4 Xa Xb induction explain Theory (nice story) Xc Xd predict Unperceivable Concepts deduction test X5
Example • This thing falls, that thing falls to the ground. • This thing falls at a different speed. Observation • Everything that is released falls to the ground. • In that case, things on the moon will fall at a different speed. Generalised Rule • Things fall because there is a gravitational force being applied to it (depending on size of attracting body). Theory
Problem about Scientific Theories • But if the predictions are correct, then the theory does not have to be right (consider the fairy tale). • Therefore, there are two kinds of problems: • We cannot verify all possible cases a theory covers. (Presented by Ladyman) (philosophy of science) • We cannot verify the theory in itself. (metaphysics)
Illustration Problem • Being ‘grue’ means being green before 2005 and blue after 2005. • Now we have a theory that says that all emeralds are ‘grue.’ • Every emerald we see seems to add up to the conclusion that this theory is correct.
Ockham’s Razor • William of Ockham’s Razor: ‘If all things are equal, the most simple explanation is the right one.’ • By the way, he was a Medieval Philosopher.
Conclusions • Scientific theories are designed to explain. • Scientific theories tend to postulate concepts that cannot be directly perceived. • Problems about induction: • We cannot verify all possible cases a theory covers. (presented by Ladyman) • We cannot verify the theory in itself.
Discussion Louis & Jessica
Science is the religion of modern societies Definition of religion(the concise Oxford dictionary): • The belief in a superhuman controlling power, esp. in a personal God or gods entitled to obedience and worship • A particular system of faith and worship • A thing that one is devoted to • Et cetera
Science is the religion of modern societies Since scientific theory in itself cannot be observed, therefore it could be just a likely explanation. It takes a leap of faith to believe that the theory is actually true.
The End • Have a nice break. • A copy of this presentation is available for downloading at http://vanvugt.cjb.net