Outline Moral Community & Moral Status
Clea F. Rees R. M. Hare, ‘What is Wrong with Slavery?’ Moral Community & Moral Status Virtue ble ss i Per mi Et h Im per m ible iss al hic Moral Immoral Outline l ica Moral Community & Moral Status Un et V i ce Outline Hare’s Thesis Moral Community & Moral Status The Challenge Hare, ‘What is Wrong with Slavery?’ Argumentation Recap Hare’s Premises Logical Structure Argument Form Dr. Clea F. Rees ReesC17@cardiff.ac.uk Centre for Lifelong Learning Cardiff University Evaluation What Makes an Argument Good? Validity: How Good is the Logic? Truth: How Good are the Premises? Soundness: How Good is the Argument? Moral Community & Moral Status Un et V i ce 1. Abortion is the deliberate killing of a human being. 2. If something is the deliberate killing of a human being, then it is wrong. Un et V i ce We noticed last time that these two arguments have the same logical form: 1. My cat enjoys a good game of tiddlywinks. 1. . 2. If my cat enjoys a good game of tiddlywinks, then tiddlywinks is a game loved by the gods. 2. If , then . —— 3. . —— That is, they have the same logical structure. 3. Tiddlywinks is a game loved by the gods. — 1 of 4 — Per mi Immoral al hic Per mi Immoral al hic ible iss Example (Argument) Un et Argument Form V i ce Argumentation Et h Im per m Im per m Argument Form Virtue ble ss i Moral Argumentation ible iss Et h l ica Moral Community & Moral Status Virtue ble ss i Moral Argument Form —— 3. Abortion is wrong. l ica Argumentation Per mi Example (Argument) Definition (Sub-Argument) A sub-argument is an argument which forms one part of a larger argument. The conclusion of a sub-argument is a sub-conclusion of the overall argument. A sub-conclusion is both a conclusion of the sub-argument and a premise in a further argument. Argument Form Immoral Argument Form Definition (Argument) An argument consists of a set of sentences of which one is the conclusion and the rest are premises. The conclusion is the claim the argument tries to convince you of. The premises are the claims which are supposed to support the conclusion. Argumentation al hic Per mi Immoral ible iss Argumentation Recap Moral Community & Moral Status Un et al hic Argument Form Im per m Argumentation Et h Moral Im per m Recap Virtue ble ss i Argumentation l ica Et h V i ce Virtue ble ss i Moral Argumentation l ica Moral Community & Moral Status ible iss Autumn 2013 Clea F. Rees R. M. Hare, ‘What is Wrong with Slavery?’ Moral Community & Moral Status Per mi Immoral al hic Per mi Immoral al hic ible iss Un et V i ce Argumentation Argument Form Example (Two Arguments — One Logical Form) Example (Two Arguments — One Logical Form) 1. My cat enjoys a good game of tiddlywinks. 1. Abortion is the deliberate killing of a human being. 1. . 1. . 2. If something is the deliberate killing of a human being, then it is wrong. 2. If , then . 2. If , then . —— —— Moral Community & Moral Status Per mi Immoral Immoral ible iss al hic What Makes an Argument Good? Im per m Im per m Un et V i ce Evaluation Et h Moral Moral What Makes an Argument Good? Virtue ble ss i Evaluation al hic Per mi Et h Un et Virtue ble ss i 3. . l ica Evaluation l ica Moral Community & Moral Status —— 3. . 3. Abortion is wrong. V i ce —— 3. Tiddlywinks is a game loved by the gods. ible iss Argument Form 2. If my cat enjoys a good game of tiddlywinks, then tiddlywinks is a game loved by the gods. Im per m Im per m Argument Form Moral Moral Argumentation Et h Un et l ica Argument Form Virtue ble ss i Argumentation V i ce Et h ible iss Virtue ble ss i Argumentation l ica Moral Community & Moral Status Evaluation What Makes an Argument Good? What Makes an Argument Good? Arguments Evaluating an Argument Ask two questions: 1. How good is the logic or reasoning? Logical Reasoning Do the premises support the conclusion? 2. How good are the premises? Good Premises Are the premises true? Per mi Immoral al hic Per mi Immoral ible iss al hic Un et Un et V i ce Evaluation Validity: How Good is the Logic? Arguments Definition (Validity) An argument is valid iff if the premises are true, then the conclusion must be true as well. Valid Reasoning Definition (Invalidity) An argument is invalid iff it is not valid. In other words, it is possible that the premises could be true and the conclusion false. — 2 of 4 — Good Arguments Good Premises Im per m Validity: How Good is the Logic? In other words, the conclusion follows from the premises. Et h Moral Validity: How Good is the Logic? Virtue ble ss i Evaluation l ica Evaluation Et h Im per m Validity: How Good is the Logic? Moral Community & Moral Status Virtue ble ss i Moral Evaluation l ica Moral Community & Moral Status V i ce I Good Arguments ible iss I R. M. Hare, ‘What is Wrong with Slavery?’ Moral Community & Moral Status Per mi Immoral Immoral al hic Validity: How Good is the Logic? Im per m Im per m ible iss al hic Et h Moral Moral Un et V i ce Evaluation Virtue ble ss i Un et l ica Validity: How Good is the Logic? Evaluation V i ce Et h ible iss Virtue ble ss i Evaluation l ica Moral Community & Moral Status Per mi Clea F. Rees Evaluation Validity: How Good is the Logic? Validity: How Good is the Logic? 1. . If two arguments have the same logical form: either 2. If , then . —— 3. . What, if anything, can we say about the validity of any argument with this form? both are valid, I both are invalid. No matter how different their content. Un et Per mi Immoral Immoral al hic Truth: How Good are the Premises? Im per m Im per m ible iss al hic Et h Moral Moral Un et V i ce Evaluation Virtue ble ss i V i ce l ica Validity: How Good is the Logic? Evaluation ible iss Et h Per mi Moral Community & Moral Status Virtue ble ss i l ica Moral Community & Moral Status Evaluation I or Evaluation Validity: How Good is the Logic? Truth: How Good are the Premises? Arguments can be valid with: Truth I some false premises and a false conclusion. I true premises and a true conclusion. I some false premises and a true conclusion. I all true premises and a false conclusion. I Moral Community & Moral Status Virtue ble ss i Per mi Et h Soundness: How Good is the Argument? ible iss Un et V i ce Evaluation Truth: How Good are the Premises? Soundness: How Good is the Argument? Arguments Valid Reasoning Good Arguments Definition (Soundness) An argument is sound iff it is valid and it has all true premises. True Premises (It follows that the conclusion must be true.) — 3 of 4 — Virtue ble ss i Et h Im per m al hic Evaluation Moral Evaluation Im per m Truth: How Good are the Premises? Moral Immoral l ica Evaluation l ica Moral Community & Moral Status Is this claim true? Per mi I An argument can be invalid with: The key question is whether the argument makes any false assumptions. For each premise which is not a sub-conclusion, ask: Immoral I The only combination not possible for a valid argument is all true premises and a false conclusion. al hic some false premises and a true conclusion. Un et true premises and a true conclusion. I V i ce some false premises and a false conclusion. I ible iss I Clea F. Rees R. M. Hare, ‘What is Wrong with Slavery?’ Moral Community & Moral Status Un et V i ce Per mi Immoral Soundness: How Good is the Argument? Definition (Unsoundness) An argument is unsound iff it is not sound. Evaluating an Argument Two ways an argument can go wrong: 1. Bad logic/reasoning. An argument is unsound iff: either I it is invalid, I at least one premise is false. or One or more premises are false. Moral Community & Moral Status Per mi Per mi Immoral al hic ible iss al hic Soundness: How Good is the Argument? Un et V i ce Evaluation Soundness: How Good is the Argument? Soundness: How Good is the Argument? Arguments Un et V i ce Soundness: How Good is the Argument? All sound arguments have: —— 3. . I true premises. I true conclusions. An unsound argument may have: What, if anything, can we say about the soundness of any argument with this form? — 4 of 4 — Per mi Immoral Immoral al hic ible iss Evaluation 2. If , then . Et h I one or more false premises and a false conclusion. I one or more false premises and a true conclusion. I all true premises and a true conclusion. Im per m Soundness: How Good is the Argument? 1. . Virtue ble ss i Moral Soundness: How Good is the Argument? Im per m Evaluation Evaluation al hic Per mi Et h Moral Soundness: How Good is the Argument? True Premises Moral Community & Moral Status Virtue ble ss i Sound Arguments l ica Evaluation l ica Moral Community & Moral Status Valid Reasoning Un et True Premises V i ce Sound Arguments Arguments ible iss Valid Reasoning Im per m Im per m Evaluation Et h Moral Moral Immoral l ica Soundness: How Good is the Argument? Virtue ble ss i Evaluation Un et Et h V i ce Virtue ble ss i Evaluation l ica Moral Community & Moral Status ible iss The argument is invalid. 2. Bad premises. I al hic Per mi Immoral al hic ible iss Evaluation Soundness: How Good is the Argument? I Im per m Im per m Soundness: How Good is the Argument? Moral Moral Evaluation Et h Un et l ica Soundness: How Good is the Argument? Virtue ble ss i Evaluation V i ce Et h ible iss Virtue ble ss i Evaluation l ica Moral Community & Moral Status
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