The Problem of Induction Dr Peter W Evans 23 April, 2013 The Problem of Induction Today Structure of logical reasoning: the problem Inductive reasoning and science Hume's analysis Naturalism Deductive reasoning All primates are mammals. All mammals are warm-blooded. ) All primates are warm-blooded. Deductive reasoning Warm-blooded Mammals Primates Deductive reasoning All primates are mammals. Koko the gorilla is a primate. ) Koko the gorilla is warm-blooded. Deductive reasoning Mammals Primates Koko Deductive reasoning All As are Bs All Bs are Cs ) All As are Cs Deductive reasoning All As are Bs x is an A ) x is a B Inductive reasoning Tarantino's `Reservoir Dogs' was graphically violent. Tarantino's `Pulp Fiction' was graphically violent. Tarantino's `Kill Bill' was graphically violent. Tarantino's `Inglourious Basterds' was graphically violent. ) Tarantino's new film `Django Unchained' will also be graphically violent. Inductive reasoning All the ravens I have seen so far have been black. ) All ravens are black. Inductive reasoning The raven I saw this morning was black. All the ravens I have ever seen have been black. All the ravens that anybody else has ever seen have been black. ) All ravens are black. Inductive reasoning All ravens that have been seen are black. All ravens have the same colour. ) All ravens are black. Inductive reasoning Inductive reasoning is fallible: some observation might show conclusion to be false. This is the problem of induction. Induction and science Scientific inquiry hostage to problem of induction: objects fall when dropped; sun will rise tomorrow. Induction and science L. Bortolotti, An Introduction to the Philosophy of Science, p 37: Take the debate about the causes of stomach ulcers in medical research. For many years researches believed on the basis of their observations that bacteria could not survive in an acid environment such as the stomach, and therefore ruled out the possibility that bacteria were the cause of ulcers. Stress and spicy food were considered the likely triggers of ulcers and recommended treatment consisted in prescribing drugs that blocked the production of acid. [A pair of researchers from Perth then] discovered that there is a bug responsible for many stomach and duodenal ulcers (Helicobacter pylori) that lives in the stomach and adapts to its harsh environment. The cure now consists in the elimination of this bug. Hume's argument The sun has risen every day up to now. ) The sun will rise tomorrow. Hume's argument The sun has risen every day up to now. Nature operates uniformly. ) The sun will rise tomorrow. Induction and scepticism Scepticism: don't really what we think we know; impossible to have knowledge concerning the unobserved world. Induction and scepticism Induction and scepticism Induction and scepticism I know that the sun will rise tomorrow in those cases where I have a belief that the sun will rise tomorrow, it turns out that the sun does in fact rise tomorrow and my belief is justified inductively regardless of whether I have ruled out every possibility that my belief is false. Even though my belief may be fallible, it is well-justified, and if it turns out to be true then I'll count it as knowledge. Induction and scepticism I don't know that the sun will rise tomorrow because I can't say with absolute certainty that it will. Nonetheless, all of the evidence that I have suggests that the sun will rise tomorrow, and I have sought contrary evidence and found none. Thus, it is rational for me to believe that the Sun will rise tomorrow. My belief is fallible, and that means that it is not knowledge, but it is still very reasonable for me to believe it, and very unreasonable for me to hold a conflicting belief. Hume's response Naturalism: philosophy should be continuous with science; begin philosophy from scientific picture of human beings and their place in the universe. Hume's response Anthropological history leads us to belief-forming behaviour: selection pressure from nature drives evolution; natural response to regularity is to believe regularity will continue. This belief employed to justify inductive inferences. Another response Salmon: prudent to bet on success of inductive reasoning; simply works better than available alternatives. Course next semester PHI2/3HPB: Philosophy of Science Image references The image on slide 2 is courtesy of Wikipedia, http://en.wikipedia.org/wiki/File:Painting of David Hume.jpg The image on slide 20 is courtesy of Wikipedia, http://en.wikipedia.org/wiki/File:2006-ca-turkey.jpg The image on slide 21 is courtesy of Flickr user Mike fleming, used under a Creative Commons license, http://www.flickr.com/photos/flem007 uk/3135502287/.