1.5: Introduction to Logic

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To attempt to try to figure out which moral views about animals are correct, we will try to find out which views are supported by the best reasons. To do this, will identify and evaluate arguments. The James Rachels (“Some Basic Points About Arguments” (Google) and James Pryor (at http://www.jimpryor.net/teaching/vocab/index.html) readings give excellent overviews of what arguments are and what makes arguments good and bad.

An argument is a conclusion that is supported by premises. The premises should lead to the conclusion, forming a “chain” of reasoning: this makes the argument “logically valid” (a technical term with a precise meaning that differs from how non- philosophers often might use the term). In a valid argument, since the premises lead to the conclusion (and this chain of reasoning is clearly identifiable), if the premises are true, then the conclusion must be true as well. When an argument is valid and the premises are true, then the argument is sound (and the conclusion is thereby true, given the definition of “valid” and the fact that the premises are true). If the argument is valid and, with good reasons, you think the premises are true, then you should think the argument is sound. We want to find sound arguments and reject unsound ones.

Our main concern is finding the arguments, understanding what exact conclusion(s) is being defended and what exact premises are given in its favor. We have to figure out whether the premises lead to the conclusion, i.e., is valid, or if we can “tweak” the argument by adding premises to make it valid. We then try to figure out if it is sound. Here are three rules for carefully identifying arguments:

Make the stated conclusion(s) and premise(s) precise in quantity: is something said to be true (or false) of all things (or people, or animals, etc.), or just some of them (and if so, which ones?)?
Clarify the intended meaning(s) of unclear or ambiguous words in conclusions or premises.
State (any) assumed premises so that the complete pattern of reasoning in an argument is displayed and it is clear how the stated premise(s) logically leads to the conclusion.

Other important logical tools are that of necessary condition(s), sufficient condition(s), necessary and sufficient condition(s), and counterexamples. (See Pryor especially). The importance of these concepts for animal ethics will be apparent as we work through the issues.