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III.9
What
is a Reasoned Argument?
Reason means truth and those who are not governed by it
take the chance that someday the sunken fact will rip the bottom out of
their boat.
Oliver Wendell Holmes, Jr. (1841-1935)
Reason is the shepherd trying to corral life's vast flock of wild
irrationalities.
Paul Eldridge (1888-1982)
So use reason with caution, and if you really want to persuade
someone of something, remember that compassion, honesty and tact
are as important as logic.
All dogs are mammals (premise) Dolly is a dog (premise) Dolly is a mammal (conclusion)
Summary: A sound or "good" argument is defined as:
a. An argument is deductively valid if and only if it is impossible that its conclusion is false while its premises are true. b. An argument is inductively strong if and only if it is improbable that its conclusion is false while its premises are true. The degree of inductive strength depends on how improbable it is that the conclusion is false while the premises are true. Also, the argument may be tested if it is deductively valid, but if so, then it is not an inductive argument. An argument, as one may conclude from the preceding, is a factual dispute or disagreement over the truth or falsity of one or more statements. It suggests the use of logic and the bringing forth of facts to make, support, or refute a point. A dispute or quarrel refers to a contradiction of an assertion and implies vehemence or anger in debate. It is often a disagreement in attitude or viewpoint on how one should feel about a factual situation or the meaning of certain words. A controversy connotes a disagreement of lengthy duration over a matter of some weight or importance. For example, pro-life (antiabortion rights) advocates vs. pro-choice (abortion rights) supporters, naturalism vs. supernaturalism, a free market economy vs. a planned one. B. What Is an Inference? We may act on probabilities when only by such action can we get the additional evidence that may justify future belief. Belief beyond evidence is permissible, but only when the proposition believed is strictly inferred from past experience on the assumption that the future will be like the past. William K. Clifford (1845-1879) An inference is a deriving of conclusions from given information or premises by any acceptable form of reasoning. Inferences are commonly acquired by:
Charles Sanders Peirce (1839-1914) He that cannot reason is a fool. He that will not is a bigot. He that dare not is a slave. Andrew Carnegie (1835-1919) First: We must determine who has the burden of proof, that is, who made the initial claim and is thus responsible for providing evidence why his assertion merits acceptance. The burden of proof (Latin: onus probandi) usually lies with the party arguing for a new claim, position, conclusion, accusation, etc. The exception to this rule is when a prima facie (self-evident) case has been made. The burden of proof may only be fulfilled by evidence. The burden of proof is an especially important issue in law and science. Second: Because the argument may be buried in a larger text, perhaps even in an entire book, we have to identify and understand the argument or arguments whether explicit or implied, and the objectives of the participants in the dialogue. Third: We identify the premises from which conclusions are derived. Fourth: We evaluate an argument--whether it be inductive, deductive, or empirical moral--by calling it sound if and only if its premises are true and if the reasoning, the inference, is valid or cogent. We use the term "valid" in the case of a deductive (it follows) argument and "cogent" (convincing) or "strong" when it is an inductive argument. Fifth: Because the truth or falsity of a proposition is often not an absolutes but a matter of degree, we have to rate these values to better measure the worth of our conclusion. See "Truth and Falsity are Matters of Degree" in Knowledge as Justified True Belief. Sixth: We have to qualify the claims of propositions according to their applicable modals. That is, we have to affirm or deny possibility, impossibility, necessity, contingency, etc. See "Modality, Qualifying the Claims of Prepositions" below. Seventh: If the argument is sound, then its premises must be:
1. The Inductively Strong Argument Inductive logic is the logic of uncertain conclusions--uncertain both in themselves and in relation to the premises from which they are inferred. Abraham Kaplan (1918-93) However, One of the most important uses of inductive logic is to frame our expectations of the future on the basis of our knowledge of the past and presents. Brian Skyrms (in Choice & Chance, 1986) But still An inductive argument is never final because it is always open to the possibility of being weakened or even falsified by future discoveries. This writer Inductive reasoning or logic is often, but not necessarily, the act or process of inducing, inferring by logical reasoning, generalizations from particular facts or a few instances. Hence, it often involves the estimation of frequencies and then extrapolating from these estimates. In sum, when we use a number of established facts to draw a general conclusion, we use inductive reasoning. This kind of logic is used when we learn from experience as we grow up, and just as it is used in this way by the sciences. However, inductive reasoning is always subject to revision if new facts are discovered, for it is by this process of induction and correction that progress is made in the sciences as well as in life. The following is an example of an inductive argument: The latest census by the Mexican government indicates that 88 percent of its citizens are Roman Catholics. Juan Garcia's documents indicate he emigrated from Mexico. Juan Garcia is probably a Roman Catholic. This cogent inductive inference produced a qualified conclusion because something is declared to be true under certain circumstances, in certain respects, and to a certain extent. In sum: A good inductive argument is one in which the premises strongly support or confirm the conclusion. Or to be more exact as Brian Skyrms observed: The type of probability that grades the inductive strength of arguments--we shall call it inductive probability--does not depend on the premises alone, but on the evidential relation between the premises and the conclusion. Another way of phrasing it is to say that inductive logic induces, leads to belief, draws or brings about, a general rule or conclusion from particular facts. The premises or collection of facts of an inductive argument support the conclusion but do not entail it, that is, the truth does not follow logically from it. A classical example from old text books is: All swans so far observed are white. Conclusion: All swans are white. This conclusion would be true if and only if all swans past, present, and future would be white. But then, after Australia was discovered, black swans were sighted. Hence, when we draw conclusions from a series of observed facts, they will always be a matter of probability and never certainty. So we hedge our conclusion and should have said in the above case: All swans are probably white. 2. The Deductively Valid Argument If one accepts the premises of a valid deductive argument as probably true or acceptable, then it would be absurd to reject its conclusion, that is, one would practice self-contradiction. This writer The deductive argument, deductive reasoning, or deductive logic is discursive, that is, one goes from premises to conclusions in a series of logical steps. This is to be distinguished from intuitive which is the act of immediate knowing or learning of something without the conscious use of reason; instantaneous apprehension; an insight. Another way of defining deductive reasoning is to say that it is the act or process of deducing, inferring by logical reasoning, specifics from known facts or general principles. These facts or general principles may have been reached by inductive reasoning. In deduction we argue sometimes, but not necessarily, from the general to the specific. For example,
All Greeks are mortal (premise) Socrates is a Greek (premise) Socrates is mortal (conclusion) This argument is of the deductive kind because it meets the following textbook definition: Deductive reasoning starts with one or more statements called premises and examines what conclusions necessarily follow from these premises. That is, the argument is deductively valid if its conclusion contains no factual claim that is not made by its premises or at least not implied by them. Hence, the deductive inference does not give us any kind of knowledge that exceeds that of the premises. And the premise are relevant if the conclusion follows from them. Studies show that when deductive reasoning is required, people are prone to commit various errors or fallacies. One major cause is the thinker's concentration on the desirability of the conclusion rather than focusing on the plausibility of the conclusion that must follow from the premises. 3. The Three Ancient Laws of Thought 1. The Law of Identity: Whatever is A is A; everything is identical to itself. 2. The Law of Non-Contradiction: Nothing can be both A and non A, that is, for all propositions p, it is impossible for both p and not p to be true. 3. The Law of the Excluded Middle: Everything is either A or non A, that is, either proposition p or not p must be true, there being no third or middle true proposition between them. D. The Empirical Moral Argument He is a true fugitive, that flies from reason, by which men are sociable. Marcus Aurelius (121-180 CE) An argument that necessarily has at least one premise that contains a value judgment and at least one more empirical-factual premise as a reason for the conclusion. For example, It is desirable to reduce the risk of colon cancer (value judgment). A diet high in fiber reduces the risk of colon cancer (empirical-factual premise). Therefore, it is desirable to have a diet high in fiber. Again, the soundness of an argument depends on the truth of its premises and the validity of its reasoning. The above is a validly reasoned deduction. That leaves to question the truth of the two premises. Assuming that the empirical-factual premise is true, that leaves the value judgment premise. Thus, the soundness of an empirical moral argument, together with the truth of its conclusion, crucially depends on the truth or objectivity of the value judgment, see Ultimate Values Justified as Moral Rights. E. Modality, Qualifying Propositions More important than the quest for certainty is the quest for clarity. Francois Gautier (b.1950) It is the concept of modality that qualifies what is affirmed or denied in propositions as possible, impossible, necessary, contingent, obligatory, and permissible. These adjectives are named modals and like terms are: eventually, formerly, can, could, might, may, and must, since they can be treated in similar ways. In particular, modals qualify, limit in some way, the truth/affirmative or falsity/denial claims of statements. More broadly speaking, modality affects the circumstances in which we take an assertion or proposition to be satisfied. possible--is all that can exist, be done, or can happen. All things that are logically not impossible are possible. A proposition that is not impossible, for example, one that is either necessary or contingent, is said to be a possible proposition. Also, to say that a proposition is possible is to say that it is not necessarily false. It follows that it is false to say that it is impossible. impossible--not capable of existing, being done, or bound to happen in this or any other world. It follows that it is false to say that an impossible proposition is necessary, possible, or contingent. necessary--A necessary true or false proposition is one that could not have been otherwise. It would have been true or false under all circumstances in our world and all possible worlds. For instance, "7 + 5 = 12" is true by logical necessity, it is a necessary proposition. The same can be said for "all green things are colored." And "7 + 5 = 13" is false by logical necessity, it is an impossible proposition. It follows that if something is necessary, then it is false to say that it is contingent or impossible. And just as it is impossible that it is not necessary. contingent--A contingently true or false proposition is one that could be otherwise depending on, for example, historical or evolutionary circumstances. For instance, it is true that today the sun is shining in northern Arizona and the U.S. consists of fifty states. Also, it is false that it is currently raining and that the U.S. consists today of 51 states. Broadly speaking, a contingent proposition is something:
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