Introduction to Philosophy-Lecture # 2 PDF

INTRODUCTION TO PHILOSOPHY Dr. Syed Ahmad Bukhari Propositions Types of Propositions; ▪Arguments ▪Premises and Conclusions ▪Recognizing Arguments ▪Analyzing Arguments ▪Paraphrasing Arguments ▪Deductive and Inductive Arguments ▪Validity and Truth ▪Problems in Reasoning PROP...

INTRODUCTION TO PHILOSOPHY Dr. Syed Ahmad Bukhari Propositions Types of Propositions; ▪Arguments ▪Premises and Conclusions ▪Recognizing Arguments ▪Analyzing Arguments ▪Paraphrasing Arguments ▪Deductive and Inductive Arguments ▪Validity and Truth ▪Problems in Reasoning PROPOSITION A statement; what is typically asserted using a declarative sentence, and hence always either true or false, although, its truth or falsity may be unknown. PROPOSITION Propositions are the building blocks of our reasoning. A proposition asserts that something is the case or it asserts that something is not. We may affirm a proposition, or deny it but every proposition either asserts what really is the case, or it asserts something that is not. Therefore, every proposition is either true or false.  There are many propositions about whose truth we are uncertain. “There is life on some other planet in our galaxy,” for example, is a proposition that, so far as we now know, may be true or may be false. Its “truth value” is unknown, but this proposition, like every proposition, must be either true or false. A question asserts nothing, and therefore it is not a proposition. “Do you know how to play chess?” is indeed a sentence, but that sentence makes no claim about the world.  Neither is a command a proposition (“Come quickly!”), nor is an exclamation a proposition (“Oh my God!”). Questions, commands, and exclamations unlike propositions are neither true nor false. Sentences are always parts of some language, but propositions are not tied to English or to any given language. ARGUMENT With propositions as building blocks, we construct arguments. In any argument we affirm one proposition on the basis of some other propositions. In doing this, an inference is drawn.  Inference is a process that may tie together a cluster of propositions. Some inferences are warranted (or correct); others are not. The logician analyzes these clusters, examining the propositions with which the process begins and with which it ends, as well as the relations among these propositions. Such a cluster of propositions constitutes an argument. Arguments are the chief concern of logic.  Argument is a technical term in logic. In logic, argument refers strictly to any group of propositions of which one is claimed to follow from the others, which are regarded as providing support for the truth of that one. For every possible inference there is a corresponding argument.  ARGUMENT In writing or in speech, a passage will often contain several related propositions and yet contain no argument. An argument is not merely a collection of propositions; it is a cluster with a structure that captures or exhibits some inference. We describe this structure with the terms conclusion and premise. The conclusion of an argument is the proposition that is affirmed on the basis of the other propositions of the argument. Those other propositions, which are affirmed (or assumed) as providing support for the conclusion, are the premises of the argument. Arguments vary greatly in the degree of their complexity. Some are very simple. Other arguments, as we will see, are quite intricate, sometimes because of the structure or formulation of the propositions they contain, sometimes because of the relations among the premises, and sometimes because of the relations between premises and conclusion. The simplest kind of argument consists of one premise and a conclusion that is claimed to follow from it. For instance; No one was present when life first appeared on earth. Therefore any statement about life’s origins should be considered as theory, not fact. Aristotle, who studied the constitution and quality of actual states in Greece more than two thousand years ago, wrote confidently in Politics, Book IV, Chapter 11: A state aims at being a society composed of equals, and therefore a state that is based on the middle class is bound to be the best constituted. In this case we do have an argument. This argument of Aristotle is short and simple; most arguments are longer and more complicated. Every argument, however—short or long, simple or complex—consists of a group of propositions of which one is the conclusion and the others are the premises offered to support it. Reasoning is an art, as well as a science. It is something we do, as well as something we understand. Giving reasons for our beliefs comes naturally, but skill in the art of building arguments, and testing them, requires practice. Who has practiced and strengthened these skills is more likely to reason correctly than one who has never thought about the principles involved. Recognizing Argument Before we can evaluate an argument, we must recognize it. We must be able to distinguish argumentative passages in writing or speech. Doing this assumes, of course, an understanding of the language of the passage. However, even with a thorough comprehension of the language, the identification of an argument can be problematic because of the peculiarities of its formulation. Even when we are confident that an argument is intended in some context, we may be unsure about which propositions are serving as its premises and which as its conclusion. As we have seen, that judgment cannot be made on the basis of the order in which the propositions appear. How then shall we proceed? Conclusion Indicators and Premise Indicators One useful method depends on the appearance of certain common indicators, certain words or phrases that typically serve to signal the appearance of an argument’s conclusion or of its premises. Here is a partial list of conclusion indicators: therefore for these reasons Hence it follows that So I conclude that accordingly which shows that in consequence which means that consequently which entails that proves that which implies that as a result which allows us to infer that for this reason which points to the conclusion that Thus we may infer Premise Indicators Other words or phrases typically serve to mark the premises of an argument and hence are called premise indicators. Usually, but not always, what follows any one of these will be the premise of some argument. Here is a partial list of premise indicators: since as indicated by because the reason is that for For the reason that as may be inferred from follows from may be derived from as shown by may be deduced from inasmuch as in view of the fact that Deductive and Inductive Arguments Every argument makes the claim that its premises provide grounds for the truth of its conclusion; that claim is the mark of an argument. However, there are two very different ways in which a conclusion may be supported by its premises, and thus there are two great classes of arguments: the deductive and the inductive. Understanding this distinction is essential in the study of logic. A deductive argument makes the claim that its conclusion is supported by its premises conclusively. An inductive argument, in contrast, does not make such a claim. Therefore, if we judge that in some passage a claim for conclusiveness is being made, we treat the argument as deductive; if we judge that such a claim is not being made, we treat it as inductive. Because every argument either makes this claim of conclusiveness (explicitly or implicitly) or does not make it, every argument is either deductive or inductive. When the claim is made that the premises of an argument (if true) provide unquestionable grounds for the truth of its conclusion, that claim will be either correct or incorrect. If it is correct, that argument is valid. If it is not correct (that is, if the premises when true fail to establish the conclusion irrefutably although claiming to do so), that argument is invalid. For logicians, the term validity is applicable only to deductive arguments. To say that a deductive argument is valid is to say that it is not possible for its conclusion to be false if its premises are true. Thus we define validity as follows: A deductive argument is valid when, if its premises are true, its conclusion must be true. In everyday speech, of course, the term valid is used much more loosely. Although every deductive argument makes the claim that its premises guarantee the truth of its conclusion, not all deductive arguments live up to that claim. Deductive arguments that fail to do so are invalid. Because every deductive argument either succeeds or does not succeed in achieving its objective, every deductive argument is either valid or invalid. This point is important: If a deductive argument is not valid, it must be invalid; if it is not invalid, it must be valid. Thank You !!!  Any Questions???