[Lecture Ten] Introduction to Logic
by Dr. Leonard Peikoff
Total Time: 2 hours, 40 minutes
Course summary: This lecture course by Dr. Leonard Peikoff provides a comprehensive introduction and overview of the study of logic. Through exercises provided to the reader and discussion of answers, the course covers definitions, syllogisms, fallacies, and the rules of generalization. It is equivalent to a university level course in logic. Read more »
In this lecture: This lecture investigates the role of analogies in logical reasoning. Dr. Peikoff contrasts the idea of analogy in literature and non-fiction writing from its role in logical reasoning and explains how to analyze it as a logical tool.
Study Guide
This material is designed to help you digest the lecture content. You can also download below a PDF study guide for the entire course.
| What is an analogy broadly construed? |
| How does analogy work in logical reasoning as opposed to literary or explanatory/pedagogical use? |
| Is analogical reasoning a separate form of reasoning? |
| How do you evaluate the quality of an analogy? |
Q&A Guide
Below is a list of questions from the audience taken from this lecture, along with (approximate) time stamps.
| 1:56:04 | Why is it that “yellow” can’t be defined while “heat” can? While it is true for both “heat” and “yellow” that their effect on the nervous system must be felt, their physical properties can be defined. |
| 1:58:23 | Is the statement “every ‘is’ implies an ‘ought'” an axiom, or can it be proved? |
| 2:00:17 | Did you literally spend two hours on the definitions you gave us several weeks ago? Would you normally go through the detailed process you outlined, or was it done for heuristic or pedagogical purposes? |
| 2:02:08 | I have a clear definition for very few concepts. Does this mean that most of my concepts float? This is something I’ve always wanted to know, but was afraid to ask. |
| 2:06:26 | Do not the meanings of some words change with application? For example, “rock and roll,” “liberal,” “conservative”? How can you maintain a consistent definition with words of this sort? Is it contextual? Is this kind of change proper? |
| 2:11:19 | Can you remember the name of the language book you referred to? |
| 2:15:45 | Did Newton commit the hasty generalization fallacy when he formulated the laws of motion without studying the motion of bodies near the speed of light? |
| 2:20:33 | Is the following dichotomy valid? 1) Lemonade is the cause of a stomach ache (that is a philosophical explanation) vs. 2) some factor in the lemonade is the cause of the stomach ache (that is the scientific explanation). Do you agree with this analysis? |
| 2:22:59 | How do you answer the charge that the syllogism is superfluous and reveals nothing new since the conclusion is obviously centered in the premises and all that is necessary is to understand the premises? Would it be that it is only syllogism that can reveal what is in the premises, that the syllogism is the very tool with which one extracts what is contained in the premises? |
| 2:25:57 | Some statements—for example “all martians are redheads”—are neither true nor false. Could you elaborate on the criteria that a statement must achieve to be either true or false? |
| 2:28:51 | Are such statements as the one you just mentioned meaningful or meaningless? |
| 2:30:03 | Earlier you used the premise “you can’t do more than you can do.” What is the status of that premise? |
| 2:31:10 | Would you say that “all cows are purple” is false? |
| 2:31:32 | “Santa Claus has a white beard”… is that meaningless? |
| 2:33:32 | Miss Rand stated “just as the child is father to the man, the nursery school is father to the university” (in essence)… would you care to explain this analogy? |
| 2:35:02 | Do you think induction will ever be reduced to the precision that deduction now has? |
| 2:38:26 | What are the pitfalls to be aware of when reading Irving M. Copi’s book on logic? |
| 2:39:17 | Where, if at all, does Ruby differ from Objectivism his book? |