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William Seager

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Y e P a g e | 1 PHLA10 Reason and Truth Exercise 1 Pg. 17 1. When is an idea or statement valid? (trick question) A statement or an idea cannot be valid; they can only be true or false. Being valid or invalid are properties of arguments, meaning that only they can be valid or invalid. Arguments can still be valid even if the premises or conclusions are obviously untrue, or if the premises and conclusion are all false. 3. Invent an example of a valid argument that has false premises and a true conclusion. Invent an example of an invalid argument that has true premises and a true conclusion. Valid argument: All dogs can fly. Jack is a dog. So Jack can fly. Invalid argument: If the dog is running, then the dog has four legs. The dog has four legs. The dog is running. 5. Which of the following argument forms is valid? Which is invalid? For each of the invalid ones, construct an example of an argument with that form in which the premises are true and the conclusion false: (a) Valid (b) Invalid If Sam lives in Wisconsin, then Sam lives in the USA Sam lives in the USA Sam lives in Wisconsin Converse (c) Invalid If Sam lives in Wisconsin, then Sam lives in the USA Sam doesn’t live in Wisconsin Sam doesn’t live in the USA Contrapositive Y e P a g e | 2 (d) Valid 7. What does it mean to say that an argument is “circular”, that it “begs the question”? Construct an example of an argument of this type different from the ones presented in this chapter. When an argument is “circular” or that it “begs the question”, it does not give you a good reason to accept the conclusion even if the premises and conclusion are true. If the premise was not accepted, then the conclusion would not be accepted either. The Earth is a planet. Therefore, the Earth is a planet. Pg. 34 1. What is the difference between deductive validity and inductive strength? Deductive validity is either valid or invalid, there is no middle ground. An argument of this type is based on whether the premises are true, which in turn indicate whether the conclusion is true. Furthermore, deductive valid arguments cannot introduce new information in the conclusion that wasn’t already there, while inductive strength arguments can conclude on things that are beyond what was in the premises. Inductive strength can either be stronger or weaker depending on the sample size and the unbiasedness of it. 2. What is the difference between induction and abduction? Induction is taking a description of a sample and extending it to things outside the sample, for example sending out polls to figure out what the country’s preference of political parties are Abduction is reaching the best explanation possible based on evidence and reasoning. 3. What factors affect how strong an inductive argument is? The factors affecting how strong an inductive are the sample size and the unbiasedness of the sample. PHLA10 Reason and Truth Exercise 2 1. Here's a little logical puzzle: you are in a strange land where everyone is either a knight or a knave. Knights always tell the truth; knaves always lie. You meet two of them, A and B. A says "we are both knaves". What are A and B? Prove it. If A is right, then he has to be lying because he said that he is a knave as well. A cannot be a knight because they cannot both be knaves or that would make his statement true. As thus, B must be a knight. A is a knave and B is a knight. 2. What are the four main characteristics of God as Aquinas understood it? Y e P a g e | 3 Aquinas characteristics of God are that he is a personal God, omnipotent (all-powerful), omniscient (all- knowing) and omni-benevolent (all-good). Aquinas’ concept of God is also known as PKG. 3. What is the primary difference between the conception of motion that Aquinas accepted and Newton's conception of motion? Aquinas’ conception of motion was that there needed to be an outside force acting on it for it to be moving and that that force had to be kept for the object to continue being in motion. Newton’s law of motion says that an object’s acceleration will not change unless acted on by a force so it could remain in uniform motion. 4. Explain why the "Birthday Fallacy" is a fallacy. The “Birthday Fallacy” is considered to be a fallacy because the second premise does not necessarily follow the first. While the first premise, every person has a birthday – a day on which he or she was born, is true, the second premise, there is a single day that is everybody’s birthday, does not mean that everybody was born on the same day. The fact that there was a cause for the beginning of events does not mean that it was the same cause for all the events. 5. What is the valid deductive logical form of a reductio ad absurdum argument? If P is false, then A is true. A is false. _______________ P is true. 6. What is the difference between necessity and contingency? Necessity means that an object exists in all possible worlds while contingency means that an object doesn’t exist in all possible worlds. 7. What is a "necessary being"? Explain in terms of possible worlds. A necessary being is something that exists in all possible worlds. It does not depend on anything for its existence at any time from the past to the present to the future. 8. Why does Sober say that certainty is in the subjective realm while necessity is objective? Certainty is about how sure the person is of themselves about a particular statement and is as such subjective. However, necessity has nothing to do with what a person thinks or believes and is therefore objective. Y e P a g e | 4 PHLA10 Reason and Truth Exercise 3 1. Explain the structure of arguments from analogy. Arguments of this sort compare two things together, the analog and the target. There must be similarities between the two for the analogy to be good. Features from the analog are compared to the target. For example, the intricate design of the universe compared to one of a watch. 2. Why might the argument from design be a very weak inductive argument? An inductive argument relies on sample size and extrapolating data from it to the broader view. In the argument that the universe was created by an intelligent being says that that data must have been seen in other universes, and then applied to ours. 3. What is the difference between theistic evolutionism and creationism according to Sober? Theistic evolutionism states that it is God who set the evolutionary process in motion. Creationism denies that evolution is able to give rise to new species and that God plays a direct role in shaping organisms. 4. What is the 2nd Law of Thermodynamics? A closed system will move from states of greater order to states of lesser order. 5. Roughly explain how natural selection works. Amongst a population, mutations will arise in the genes at random which may or may not be advantageous. This affects the fitness of the organism. If it is advantageous and allows the organism to better survive, its chances of reproduction improve and these genes are thus passed on to the next generation. 6. An important concept in the theory of evolution is that of fitness. What is fitness? Fitness is an organism’s ability to survive and reproduce. 7. Give a new example of a correlation with a common cause. A dog starts to bark and then a few minutes later the doorbell rings. When the dog doesn’t bark the doorbell doesn’t ring. There may be a correlation between when the dog barks and when the doorbell rings. Y e P a g e | 5 8. What is "the tree of life"? All living things are related to each other, being descendent of a common ancestor. PHLA10 Reason and Truth Exercise 4 1. Why does Sober say that proving existence from a concept or definition is "very surprising"? A definition of concept only explains what characteristics something would have if it existed, not that it does in fact exist. 2. What is the difference between conceivability and possibility? Possibility is an objective point of view. It does not matter whether people believe it or think it to be true. Conceivability is a subjective point of view. 3. Why is the "perfect island" a problem for the ontological argument? The “perfect island” is showing that the ontological argument is wrong through reductio ad absurdum. By replacing “God” with “P-island” and “being” for “island”, Gaunilo tries to deduce that: A P-island is by definition the greatest possible island. An island that fails to exist in the actual world (while existing in other possible worlds) is less perfect than an island that exists in all possible worlds. __________________________________________ Hence, a P-island exists necessarily. The existence of a perfect island cannot be determined a priori and as such, neither can the existence of God through the ontological argument. 4. Try to give three clear examples of analytic truths and
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