I’m writing my next fallacy book and will be posting the text as I complete it.
If you are familiar with my 76 Fallacies, you will recognize this book as a major upgrade to its predecessor. I have added a new section on argument basics, included a brief discussion on bad faith reasoning, provided some useful general inductive arguments that commonly end up being used fallaciously, and added fallacies. I have also overhauled and re-written the 76 fallacies.
As the title indicates, this book presents numerous fallacies. The focus is on providing the reader with definitions and examples of these common fallacies rather than being a handbook on winning arguments or a detailed guide to logic. But understanding fallacies does require understanding the basics of arguments.
While people have a general idea of what “argument” means, the term also has a technical meaning. Philosophically, an argument is a set of claims, one of which is supposed to be supported by the others. In general terms, a claim is a statement that is either true or false. An argument is composed of two types of claims: one or more premises and a single conclusion.
The conclusion is the claim that is supposed to be supported by the premises. An argument has only one conclusion, though that claim can be re-used as a premise in another argument (forming an extended argument).
To find a conclusion, ask “what is the point?” If there is no point being made, then there is no argument. If a point is being made, then there can be an argument present. But an argument requires more than just a point. An argument must also have at least one premise.
A premise is a claim given as evidence or a reason for accepting the conclusion. Aside from practical concerns, there is no limit to the number of premises in an argument. To find a premise ask, “what evidence or reasons are given for the point being made?” If there is no evidence or reason being offered, then there is no argument.
Creating an argument thus requires making a point (conclusion) and backing it up with evidence or reasons (premises). In philosophy, arguments come in two main varieties: inductive and deductive.
In philosophy, there are two main categories of arguments: inductive and deductive. An inductive argument is one in which the premises are intended to provide some degree of support but less than complete support for the conclusion.
A deductive argument is one in which the premises are intended to provide complete support for the conclusion. Other fields define “induction” and “deduction” differently, but being a philosopher, I use the philosophical definitions.
A third “type” of argument is the logical fallacy. As an argument, a fallacy is an argument in which the premises fail to provide adequate support for the conclusion. There are informal fallacies and formal (deductive) fallacies. The term “fallacy” is also often used to refer to an error in reasoning, a mistaken belief, and various rhetorical techniques.
A Valid Deductive Argument
Premise 1: If Bill is a cat, then Bill is a mammal.
Premise 2: Bill is a cat.
Conclusion: Bill is a mammal.
A Strong Inductive Argument
Premise 1: 70-80% of humans have brown eyes.
Premise 2: Sally is a human.
Conclusion: Sally has brown eyes.
An Extended Deductive Argument
Argument1 Premise 1: If pornography has a detrimental effect on one’s character, it would be best to regard it as harmful.
Argument 1 Premise 2: Pornography has a detrimental effect on one’s character.
Argument 1 Conclusion: It would be best to regard pornography as harmful.
Argument 2 Premise 1: If it is best to regard something as harmful, then the government should protect people from it.
Argument 2 Premise 2: It would be best to regard pornography as harmful (conclusion of argument 1).
Argument 2 Conclusion: The government should protect people from pornography.
Informal Fallacy (Circumstantial ad hominem)
Premise 1: Dave supports the tax reduction for businesses and says it will be good for everyone, but he owns a business.
Conclusion: Dave must be wrong about the tax reduction.
An Informal Inductive Fallacy (Hasty Generalization)
Premise 1: Having just arrived in Ohio, I saw a white squirrel.
Conclusion: All Ohio squirrels are white.
A Factual Error
Columbus, Ohio is the capital of the United States.
A Formal Deductive Fallacy (Invalid Argument, Affirming the Consequent)
Premise 1: If Portland is the capital of Maine, then it is in Maine.
Premise 2: Portland is in Maine.
Conclusion: Portland is the capital of Maine.
(Portland is in Maine, but Augusta is the capital.)
Like everything else, arguments are subject to assessment. When creating an argument, the usual goal is to make a good one. When assessing an argument, the goal is to determine whether it is good.
When assessing any argument there are two factors to consider: the quality of the premises and the quality of the reasoning (logic).
While people often blend the two together, the quality of the reasoning is distinct from the quality of the premises. Just as it is possible to cook poorly using excellent ingredients, it is possible to reason badly using good premises. Also, just as it is possible for a good cook to skillfully prepare a meal using poor ingredients, it is possible to reason well using poor premises. As another analogy, consider a checkbook. Doing the math is the reasoning, getting the checks and deposits correct is like having true premises. The math can be done correctly (good reasoning) but the information entered for the checks (the premises) can be mistaken. For example, a person might accidentally enter $5 for a $50 deposit to a $100 balance but do the math right, calculating a $105 balance. It is also possible to enter all the numbers correctly, but for there to be errors in the mathematics.
When assessing the quality of reasoning, the question to ask is: Do the premises logically support the conclusion? If the premises do not logically support the conclusion, then the argument is flawed, and the conclusion should not be accepted based on the premises provided. The conclusion may, in fact, be true, but a flawed argument gives you no logical reason to believe the conclusion because of the argument in question. Hence, it would be a mistake to accept it for those reasons. If the premises do logically support the conclusion, then you would have a good reason to accept the conclusion, on the assumption that the premises are true or at least plausible.
The way the reasoning is assessed depends on whether the argument is deductive or inductive. If the argument is deductive, it is assessed in terms of being valid or invalid. A valid argument is such that if the premises were true then the conclusion must be true. An invalid argument is such that all the premises could be true and the conclusion false at the same time. Validity is tested by formal means, such as truth tables, Venn diagrams, and proofs. If an argument is valid and has all true premises, then it is sound. Naturally, a sound deductive argument also has a true conclusion. If a deductive argument is invalid, has one or more false premises (or both) it is unsound.
While deductive arguments are assessed in strict “black and white” terms (valid or invalid, sound or unsound), inductive arguments are assessed in terms of varying degrees of strength.
A strong inductive argument is an argument such that if the premises are true, then the conclusion is likely to be true. A weak inductive argument is an argument such that even if the premises are true, the conclusion is not likely to be true. There are various degrees of strength and weakness that express a somewhat subjective opinion of how well the argument’s premises logically support the conclusion. Such assessments are based on the standards for assessing the specific type of argument and the better the argument succeeds at meeting the standards, the stronger the argument. The worse it fails, the weaker the argument. A strong inductive argument with true premises is often called cogent.
One feature of inductive logic is that even a strong inductive argument can have a false conclusion even when all the premises are true. This is because of what is known as the inductive leap: with an inductive argument, the conclusion always goes beyond the premises. However, this does not make all inductive reasoning fallacious (although it does make it all technically invalid). An inductive fallacy occurs when an argument’s premises do not adequately support the conclusion. In most fallacies, this occurs because the premises being offered have little or no logical connection to the conclusion.
When assessing the quality of the premises, the question to ask is: are the premises true (or at least plausible)? While the testing of premises can be a rather extensive matter, it is reasonable to accept a premise as plausible if it meets three conditions. First, the premise is consistent with your own observations. Second, the premise is consistent with your background beliefs and experience. Third, the premise is consistent with credible sources, such as experts, standard references, and textbooks. It should be noted that thoroughly and rigorously examining premises generally involves going far beyond the three basic standards presented here.