Rhetorical fallacies, or fallacies of argument, prevent the open, two-way exchange of ideas that is required for productive interactions. Instead of employing logical argument, they divert the reader with numerous appeals. Ethical flaws unfairly boost the writer's authority or character. Psychological tricks make readers feel uncomfortable, so they try to avoid situations that trigger these feelings.
The term "rhetorical device" is often used interchangeably with "rhetorical fallacy." However, a rhetorical device is a technique or method used in rhetoric to express ideas and arguments. Common examples include comparisons, metaphors, similes, analogies, pyramids, and lists. Rhetorical fallacies are devices that are used instead of logical arguments; as such they are not true techniques in themselves but rather ways of expressing oneself.
Some scholars divide rhetorical devices into three groups: indicia, which indicate some truth of matter; figures of speech, which express something other than its literal meaning; and tropes, which represent people, places, things, or ideas and their combinations.
Indicia are evident signs that something is correct or true. For example, when arguing that gun control laws should be passed to prevent violence, it would be appropriate to mention the recent shooting incidents that caused many people to call for action. This would be an indication that such shootings do happen and they can be prevented by controlling access to guns.
Fallacies are incorrect beliefs based on flawed reasoning. While rhetorical devices can effectively persuade an audience, fallacies rely only on the appearance of logic to persuade you to agree with a flawed or wrong conclusion.
The classic example of a fallacy is called "appeal to popularity," which is when someone assumes that what most people believe must be true. For example, if many people say that trees are important then trees must be important too. This appears to be a reasonable argument until you think about it for just a minute - how could what many people believe be true? Trees are clearly important to some people and not important to others. Yet this type of argument tries to make them important anyway by using this logical fallacy.
There are several other common fallacies including affirming the consequent, ad populum, appeal to authority, and abuse of statistics. It's important to understand these concepts because they are used in political debates quite often. For example, if one politician says that his opponent's plan will cause poverty while another says it won't then which one is correct? They both seem to be arguing using logic but actually each one is using a fallacy. The first politician is appealing to popularity (what many people think) instead of examining the details of his opponent's plan. The second politician is assuming that because many other people have said something it must be true!
Rhetorical devices, in addition to supporting evidence, are employed to bolster an argument. Logical fallacies are employed as evidence in an argument and weaken it. Thus, they are rhetorical devices.
Logical fallacies include but are not limited to: ad hominem attack, appeal to emotion, begging the question, circular reasoning, group think, illogical conclusion, irrelevant comparison, nitpicking, post hoc fallacy, popular opinion, slippery slope, speculative argument, taking things out of context, three-card monte, and wrong example.
Some logical fallacies are common to more than one discipline or school of thought and thus can be considered errors rather than fallacies per se. For example, a reductio ad absurdum is used in logic and argumentation theory to show that a proposition is likely false by showing what would have to be true for it to be false. Such errors include affirming the consequent (from which its name is derived), denying the antecedent, and equivocation (changing meaning of words in course of arguing).
Others are unique to certain disciplines or schools of thought and thus should not be regarded as errors.
A rhetorical device is a device that employs words to convey meaning or convince someone to believe in a particular manner. Logical fallacies are logical flaws that can influence how someone thinks or feels about something. Although both fallacies and rhetorical devices exist, not all people who employ fallacious reasoning do so with the intention of misleading others.
Some examples of rhetorical devices include using parallel structures (i.e., subject + verb), oxymorons (i.e., bright easy to understand), and hyperboles (i.e., saying something is the greatest thing since sliced bread). Some examples of logical fallacies include argument from authority, appeal to emotion, and post hoc ergo propter hoc (i.e., if something happens after another thing then it must have been because of the other thing). Rhetorical devices and logical fallacies can be used together in a sentence or paragraph to increase its effectiveness at convincing readers.
For example, when arguing that gun control should be passed to decrease crime, an advocate might use hyperbole by saying that gun rights are the first amendment right to protect against government tyranny. This would be a case of employing a rhetorical device because it makes a strong impact without being vulgar or offensive.
Rhetorical questions are written in such a manner that they direct the reader to a specific answer or reaction. Rhetorical questions are a typical example of a flawed argument, often known as a "logical fallacy."
Logical fallacies occur when we try to prove or disprove a statement by arguing directly from its parts or using incomplete information. For example, when we argue that all men are mortal because some men are mortal, we have committed the logical fallacy of affirming the consequent. This error can also be called "the old chestnut" because it is so common when teaching logic.
The classic definition of a rhetorical question is a question that asks for a reply that itself is not explicit in the text. Thus, a rhetorical question can be answered by looking at other parts of the text or by guessing. For example, when I ask you whether John is smart, you cannot give me a fact-based answer; instead, you can only guess between Mark and Jeff by reading their profiles. Even if you think you know the right answer, you're still committing an error when you respond to a rhetorical question.
In academic writing, the term "rhetorical question" usually refers to a question that is used to draw attention to an idea without asking readers to accept it immediately.