The Elements of Science What Do Scientists Do Scientists observe what happens in the world True Mendel observed a pattern in the inheritance of traits in peas Halley observed a pattern in the occurrence of a comet But they do much more Mendel proposed factors which accounted for traits Halley proposed an orbit for comets Such proposals go beyond what is observed They attempt to explain why things happen as they do Hypotheses and Theories A hypothesis is a conjecture about the way some phenomenon in the world is or behaves Malaria is transmitted by mosquitoes Mental imagery uses the same brain processes as perception A theory is a systematic set of hypotheses Newton s theory of motion Freud s psychodynamic theory Darwin s theory of evolution 1 It is just a theory Hypotheses and theories range from conjectures or guesses to wellwell substantiated claims When first proposed most hypotheses are conjectures or proposals proposals guesses as to how things might be What matters is whether appropriate evidence can be marshaled for them Hypotheses and theories that were once wellwell substantiated may turn out to be false The theory that the sun circled the earth was once very well supported Because hypotheses and theories go beyond the evidence they always risk being falsified by future evidence Predictions and Explanations We value hypotheses and theories because they give us power and satisfy our curiosity Predictions specific detectable phenomena which we can infer from the hypothesis and to which an hypothesis is committed false predictions count against the truth of a hypothesis From the hypothesis that mosquitoes transmit maleria we predict that if we eliminate mosquitoes we will stop the spread of malaria Explanations enable us to understand why something happens and often to alter it From the hypothesis that a disease is produced by a vitamin defiency we can figure out how to treat it Representations and Phenomena Although it is the phenomenon in nature that interest us we understand it by rere presenting it to ourselves Representations are particularly important when our hypothesis and theories go beyond what we can observe to posit factors responsible for what we observe Words and sentences provide one way of representing Diagrams provide another Sometimes physical models are used All representations emphasize some features of the phenomena and distort others True of English as well 2 Statements Atoms of representation A statement is a sentence that has a truth value it is either true or false even if we do not know which A statement has an internal structure subject predicate etc but for our purposes we will not go inside of a statement Treat statements as atoms indivisible While we won t divide them we can compose them using connectives such that the truth value of the compound is determined solely by the truth value of the components AND true if both components are true OR true if at least one of the components are true IF THEN true unless the first component is true and the second false Types of statements Contingent statements Contradictions Tautologies Definitions Definitions Vastly overrated Definitions attempt to provide the necessary and sufficient conditions for being an instance of a word Example an odd number is a positive integer that is not divisible by two without remainder A necessary condition is a condition which must be met for something to be an instance of the term Being an positive integer is necessary for being an odd number A sufficient condition is one which suffices for being an instance Being both a positive integer and not being divisible by two is sufficient for being an odd number Sufficient conditions are interesting when there are different ways of satisfying a term different ways that suffice to be a U S citizen 3 Trying to define ordinary terms Necessary and sufficient conditions can generally only be provided for technical terms e g in mathematics or in legal contracts Most ordinary terms defy such definition For any attempted definition a counter example can be found A counter example is either An example that fits the definition but we would not count as an instance of a term Or An example that does not fit the definition but we would count as an instance of a term Define game Define bird Flying Not all birds fly and most insects do Feathers is everything with feathers a bird Caudipteryx Microraptor seem to have had feathers but not be birds 4 The case of color terms Central colors red blue green etc Although many others have names they are longer and not well known Boundaries less important than focal instance Doing without definitions Using examples and similarity start with typical cases Robin Chickadee Blue jay Finch Extend to unusual cases Arguments and justification If someone asserts something which you do not believe you frequently ask them to justify what they say An argument is a set of statements some of which are offered as support for other statements in the set An argument provides reasons to believe something An argument need not involve another person you can construct an argument to demonstrate that something is true without showing it to anyone 5 Premises and Conclusions The statements offered in support are called premises Often indicated by words such as Because Since Given that On account of etc The statements that are supported are called conclusions Often indicated by words such as thus therefore this establishes that etc Good and bad arguments Our concern is not just with whether the conclusion is true It is with whether those reasons stated in the premises give us good logical grounds for thinking that the conclusion is true The goal is not actual persuasion people can be persuaded for bad reasons but establishing the truth Two factors relevant to the evaluation of arguments 1 Are the premises true 2 Is the connection between the premises and the conclusion such that the premises if they were true they would establish the conclusion Valid Arguments A valid argument is an argument in which if the premises were true the conclusion must also be true A valid argument cannot have true premises and a false conclusion This relationship is modal it tells us what would be the case were certain conditions to be met These conditions might not be satisfied and the modal definition tells you nothing about what happens when they are not satisfied One way to test whether an argument is valid is to use your imagination and see if