On the Relationship of Logical and Conceptual Fallacies

In “Conceptual Fallacies and How to Avoid Them,” I mentioned the essential difference between logical and conceptual fallacies—one being a violation of the principles of logic, the other a violation of the principles of concept-formation. Here, I’d like to elaborate on their differences and similarities.

Logical fallacies are errors in the use of propositions or the drawing of inferences. (Fundamentally, they’re violations of the laws of identity, causality, and non-contradiction.) They can pertain either to deduction (the process of drawing conclusions from given premises) or induction (the process of drawing generalizations from observations). Fallacies of deduction are called “formal fallacies,” as they apply exclusively to the form of the argument. Those of induction are called “informal fallacies,” as they pertain not only to the form but also to the content and assumptions of an argument.

Formal fallacies include:

• Affirming the consequent, which consists in concluding that if one thing implies another, then that other thing implies the first thing (e.g., “If the U.S. imposes tariffs, the economy will improve; the economy has improved; therefore, the U.S. imposed tariffs.”)

• Denying the antecedent, which consists in concluding that if one thing implies another, then the absence of the first implies the absence of the other (“If government increases minimum wage, unemployment will rise; government hasn’t increased minimum wage; thus, unemployment won’t rise.”)

• Undistributed middle, which consists in concluding that if two classes of things have a characteristic in common, they are the same thing (“Natural laws impose restrictions; political laws impose restrictions; therefore, political laws are natural laws.”)

The errors involved in such fallacies lie exclusively in the form or structure of the argument—regardless of the truth or validity of the premises.

Informal fallacies, by contrast, involve drawing conclusions on the basis of insufficient information, irrelevant information, false assumptions, or unfounded assumptions.

For instance:

• Ad hominem consists in attempting to discredit an argument by verbally attacking the person making the argument, rather than addressing the argument itself (e.g., “You don’t have a degree in neuroscience or philosophy, so your views on free will carry no weight.”)

• Appeal to authority consists in arguing that a claim is true (or false) because some authority or expert on the subject said so (“Sam Harris, a neuroscientist, says free will is an illusion, so it is.”)

• A straw man fallacy consists in misrepresenting an idea or argument and attacking that fabricated version instead of the actual version (“Ayn Rand’s theory of free will holds that people have complete control over their minds—as if we can choose every thought that arises in our head. Ha!”)

The errors involved in informal fallacies lie not in the form of the argument, but in its premises—whether explicit or implicit (e.g., “Only experts’ views carry weight.”).

Both formal and informal logical fallacies treat a given argument as supporting (or undermining) a position when, in fact, it doesn’t.

Conceptual fallacies, by contrast, pertain not to arguments as a whole, but, more granularly, to the formation or use of concepts—the fundamental building blocks of arguments (and of thinking in general).

For instance:

• Package-dealing consists in combining superficially similar but essentially different things under the same term, thus obscuring crucial distinctions (e.g., conflating “majority rule” and a “rights-protecting social system” under the term “democracy”).

• The fallacy of the frozen abstraction consists in falsely equating a particular conceptual concrete with the wider abstract class to which it belongs (e.g., equating “morality” with “altruism”).

• Concept-stealing consists in using a concept while denying or ignoring a more basic concept on which it depends for its meaning (e.g., claiming that “thinking” could exist apart from a thinker).

Both logical and conceptual fallacies are errors in reasoning, but they operate at different levels. Logical fallacies occur at the level of arguments, premises, and conclusions. Conceptual fallacies occur at the level of concepts: the basic units of thought—the units of which arguments, premises, and conclusions are made.

The relationship between logical and conceptual fallacies reflects the interdependence of logic and concepts. Logic can’t proceed without concepts—as premises and inferences consist of concepts (even numbers and variables are held in the form of concepts). Likewise, the correct formation and use of concepts depends on logic. For instance, per the law of excluded middle, a thing either has a given essential characteristic in some measure or degree, or it doesn’t; if it has the characteristic, then it properly is included under the concept formed to capture such things; if it doesn’t, it isn’t. (For details, see Ayn Rand’s Introduction to Objectivist Epistemology.)

In sum, concepts are the basic units by means of which logic proceeds—and logic guides the processes by which we (correctly) form and use concepts. Each domain involves principles to guide mental action for the purpose of keeping our ideas connected to reality. And violations of the principles in either domain are fallacies of that domain.

Understanding the principles and fallacies in each area enables us to think better, live better, and defend our values more effectively. So, a big thank-you to Aristotle, Ayn Rand, and the sundry thinkers in between, who figured this stuff out. If only more people understood it.

You know what to do . . .