Logic

A lot of the problems with convincing people on Facebook or out in the real world is due to false or faulty logic also called Fallacies.

Fallacies

A fallacy is a particular type of error in deductive and inductive arguments We may expand the term to include categories of errors in reasoning or persuasive techniques (rhetoric) that lead to untrustworthy, unsound, and improbable conclusions.

A Formal Fallacy is where facts are sequenced incorrectly or missing or false facts are inserted to take the place of the truth. It is an error of logic: the conclusion is not supported by the premises. Either the premises are untrue or the argument is invalid for lack of logical form. The form of the argument is wrong or missing a truthful premise, rendering the argument as nonsense.

Informal Fallacy

An Informal Fallacy denotes an error in what you are saying, that is, the content of your argument is in error. The ideas might be arranged correctly, but something you said isn’t quite right. The content of the argument is wrong or it is out of place.

Following is a list of informal fallacies that are most commonly encountered in discussion and debate.

• Ad Hominem is attacking the character or circumstances of an individual who is advancing an argument instead of the truth of the statement or the soundness of the argument.
• Strawman Argument is an argument against an argument that was not presented.
• Appeal to Ignorance is to argue that a conclusion must be true, because there is no evidence against it.
• False Dilemma is a type of informal fallacy in which something is falsely claimed to be an "either/or" situation, when in fact there is at least one additional option.
• Slippery Slope Fallacy in logic, critical thinking, political rhetoric, and caselaw, is a logical fallacy in which a party asserts that a relatively small first step leads to a chain of related events culminating in some significant effect.
• Circular reasoning is a logical fallacy in which the reasoner begins with what they are trying to end with. The components of a circular argument are often logically valid because if the premises are true, the conclusion must be true.
• Hasty Generalization is a conclusion about all or many instances of a phenomenon that has been reached on the basis of just one or just a few instances of that phenomenon. It is an example of jumping to conclusions.
• Red Herring Fallacy unlike the straw man, which involves a distortion of the other party's position, the red herring is a seemingly plausible, though ultimately irrelevant, diversionary tactic. A red herring is something that misleads or distracts from a relevant or important question.
• Tu Quoque, (you also) the appeal to hypocrisy, is an informal fallacy that intends to discredit the opponent's argument by asserting the opponent's failure to act consistently in accordance with its conclusions
• The questionable cause—also known as causal fallacy, false cause, or non causa pro causa ("non-cause for cause" in Latin)—is a category of informal fallacies in which a cause is incorrectly identified.
• Correlation fallacy, in statistics, many statistical tests calculate correlations between variables and when two variables are found to be correlated, it is tempting to assume that this shows that one variable causes the other.
• Fallacy of Sunk Costs (or Concorde fallacy) is the fallacy that investments (i.e., sunk costs) justify further expenditures. The sunk cost effect (or Concorde effect) is the fact that behaviour often follows the sunk cost fallacy; people demonstrate "a greater tendency to continue an endeavour once an investment in money is made. In other words, a sunk cost is a sum paid in the past that is no longer relevant to decisions about the future.
• An argument from authority (argumentum ab auctoritate), also called an appeal to authority, or argumentum ad verecundiam, is a form of defeasible argument in which the opinion of an authority on a topic is used as evidence to support an argument. It is well known as a fallacy, though some consider that it is used in a cogent form when all sides of a discussion agree on the reliability of the authority in the given context. Other authors consider it a fallacy to cite an authority on the discussed topic as the primary means of supporting an argument.
• The fallacy of equivocation is where you use a word with multiple meanings such that one meaning applies to one part of an argument and another meaning applies in another part of the argument, but it’s treated as though the meaning is the same.
• An appeal to pity (also called argumentum ad misericordiam, the sob story, or the Galileo argument) is a fallacy in which someone tries to win support for an argument or idea by exploiting his or her opponent's feelings of pity or guilt. It is a specific kind of appeal to emotion. The name "Galileo argument" refers to the scientist's suffering as a result of his house arrest by the Inquisition.
• The Bandwagon fallacy based on the assumption that the opinion of the majority is always valid: that is, everyone believes it, so you should too. It is also called an appeal to popularity, the authority of the many, and argumentum ad populum (Latin for "appeal to the people").

Formal Fallacy

Aristotelian fallacies

• Fallacy of four terms (Quaternio terminorum);
• Fallacy of the undistributed middle;
• Fallacy of illicit process of the major or the minor term;
• Affirmative conclusion from a negative premise.

Affirming the consequent or fallacy of the converse or confusion of necessity and sufficiency,

Affirming a disjunct

Affirming a disjunct is a form of argument in which one disjunct of a disjunctive premiss is affirmed as a premiss, while the other disjunct is denied as a conclusion.

1. Max is a mammal or Max is a cat.
2. Max is a mammal.
3. Therefore, Max is not a cat.

Fallacy of the undistributed middle

This is a form of non sequitur which is a conclusion or statement that does not logically follow from the previous argument or statement.

Denying the antecedent

1. If A is true, then B is true.
2. A is false.
3. Therefore, B is false.