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The Amateur Logician Tutorial:
An Invitation | Arguments | Evaluating Arguments | Laws of Thought | Ontology & Logic | Concepts, Signs, & Names | Categorical Propositions | Negations & Complements | Distribution | Euler’s Circles & Venn Diagrams | Predicables | Categories | Definitions | Square of Opposition | Equivalent “Immediate Inference” | Traditional “Immediate Inference” | Informal “Immediate Inference” | Categorical Syllogism | Syllogisms & Venn Diagrams | Moods & Figures of Syllogisms | Polysyllogisms & the Sorites | Enthymemes | Compound Propositions | Conditional Propositions & Conditional Syllogisms | Conditional Contrapositions, Reductions, & Biconditionals | Conjunctions, Disjunctions, & Disjunctive Syllogisms | Dilemmas | Modal Propositions | Reductio ad Absurdum Arguments | Deduction & Induction | Inductive Abstraction | Inductive Syllogisms | Mill’s Inductive Methods | Science & Hypothesis | Formal Fallacies | Testimony & Unsound Authority | Informal Fallacies & Language | Diversion & Relevancy Fallacies | Presumption Fallacies | Causal & Inductive Fallacies
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Logic allows you to “declare your independence.”
It strengthens your ability to evaluate arguments and theories on your own.
A Brief Introduction to Argumentation
An Argument . . .
It contains a conclusion: the conclusion declare something to be the case
It contains premises: these provide evidence for the conclusion
Logic might not be exactly identical to “critical thinking,” depending on how we define these terms, though it’s surely related. Logic is largely the study of argumentation.
However a mere claim by itself is not an argument; it is only a claim. The question is: is a claim true or likely true? To evaluate it, we need to answer the “why” question: why is the given claim true or likely true?
There needs to be evidence, which should be linked to the claim in a logical way so as to justify it. Such a “claim” is something that can be said, in theory, to be true or false. It is truth-relational in that it is a declaratory judgement about something, not a wish, command, or question.
Arguments have two basic parts: premises and a conclusion. The conclusion is the claim that is being argued for. An argument’s premises are used to justify that conclusion. They provide the evidence.
Patrick Hurley, the author of a widely-used contemporary logic textbook, writes: “The evaluation of arguments involves two steps: evaluating the link between premises and conclusion, and evaluating the truth of the premises” (p 70).
Hence when someone is arguing that a certain claim is true, that claim is a conclusion to an argument with declared premises. These premises are their own truth-relational declaratory judgements, and they are taken (or argued) as true to help justify the conclusion. The process by which the conclusion is derived from these premises is a matter of inference.
To claim that “Socrates is mortal” follows from the premises that “all men are mortal” and that “Socrates is a man” is an example of inferring. Though such an argument as this is intuitively obvious, it is based on the foundation of good logic. It answers the question: “Why is Socrates mortal?” The answer is that he is a man and that all men are mortal.
Logic is necessary but not sufficient, though. It cannot tell us that “all men are mortal” or that “Socrates is a man.” Using logic helps ensure that the arguments are valid, i.e., that the conclusion follows from the given premises. Thus a valid argument’s conclusion can be false by having at least one false premise.
“Formal logic” deals with general or universal laws of good reasoning. It deals with valid reasoning. This cannot be emphasized enough. Logic abstracts away concrete matter or concrete content to search for general “forms” or “patterns” of good argumentation.
This is what makes formal logic a “science.”[1]
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[1] The term “science” had a far broader definition than the typical connotation today. It was traditionally never limited to physics, chemistry, or biology. A science is over a specific subject matter that can be studied in an organized, systematic manner, based on some “first principles” or assumptions to launch this search, which looks for underlying causes and/or principles through a specific method of discovery. Thus, logic is a science.