When you encounter a claim, an opinion, or a recommendation, how do you evaluate its validity, reliability, and relevance? Critical thinking is the skill of analyzing and assessing different arguments, using logic, evidence, and criteria. In this article, you will learn about some common types of arguments, their strengths and weaknesses, and how to spot fallacies and biases.
Deductive arguments are based on premises that are supposed to guarantee the truth of the conclusion. For example, if all humans are mortal and Socrates is human, then Socrates is mortal. Deductive arguments are strong when they are valid and sound. Validity means that the conclusion follows necessarily from the premises, regardless of whether they are true or not. Soundness means that the premises are true and the argument is valid. Deductive arguments are weak when they are invalid or unsound. Invalidity means that the conclusion does not follow necessarily from the premises, even if they are true. Unsoundness means that one or more of the premises are false or doubtful.
Inductive arguments are based on premises that are supposed to make the conclusion probable or likely, but not certain. For example, if most birds can fly and Tweety is a bird, then Tweety can fly. Inductive arguments are strong when they are cogent and reliable. Cogency means that the premises are true and relevant, and that they support the conclusion with a high degree of probability. Reliability means that the argument is based on sufficient and representative evidence, and that it avoids hasty generalizations, cherry-picking, or confirmation bias. Inductive arguments are weak when they are uncogent or unreliable. Uncogency means that the premises are false or irrelevant, or that they do not support the conclusion with a high degree of probability. Unreliability means that the argument is based on insufficient or unrepresentative evidence, or that it commits hasty generalizations, cherry-picking, or confirmation bias.
Abductive arguments are based on premises that are supposed to make the conclusion the best explanation for a given phenomenon or observation. For example, if you see smoke coming from a building, you may infer that there is a fire inside. Abductive arguments are strong when they are plausible and parsimonious. Plausibility means that the conclusion is consistent with the available facts and background knowledge, and that it does not contradict other established theories or hypotheses. Parsimony means that the conclusion is the simplest and most economical explanation, and that it does not introduce unnecessary assumptions or entities. Abductive arguments are weak when they are implausible or unparsimonious. Implausibility means that the conclusion is inconsistent with the available facts or background knowledge, or that it contradicts other established theories or hypotheses. Unparsimony means that the conclusion is the most complex and costly explanation, and that it introduces unnecessary assumptions or entities.
Ethical arguments are based on premises that are supposed to make the conclusion morally right or wrong, good or bad, desirable or undesirable. For example, if killing innocent people is wrong and war kills innocent people, then war is wrong. Ethical arguments are strong when they are coherent and universalizable. Coherence means that the premises and the conclusion are based on the same moral principles or values, and that they do not involve any contradictions or inconsistencies. Universalizability means that the premises and the conclusion can be applied to any similar situation or case, and that they do not involve any double standards or exceptions. Ethical arguments are weak when they are incoherent or non-universalizable. Incoherence means that the premises and the conclusion are based on different or conflicting moral principles or values, or that they involve any contradictions or inconsistencies. Non-universalizability means that the premises and the conclusion cannot be applied to any similar situation or case, or that they involve any double standards or exceptions.
Fallacies and biases are errors or flaws in reasoning that undermine the strength and validity of an argument. Fallacies are mistakes in logic, such as circular reasoning, slippery slope, false dilemma, or ad hominem. Biases are prejudices or preferences that affect the evaluation of evidence, such as confirmation bias, availability bias, anchoring bias, or hindsight bias. Fallacies and biases can be intentional or unintentional, conscious or unconscious, but they always impair the quality and credibility of an argument. To avoid fallacies and biases, you need to be aware of them, check your sources and assumptions, and seek feedback and counterarguments.
Politicians rely on these fallacies to further their agendas. It would be great if the voting public were aware of them and their damaging rhetoric. For instance, a false dilemma, “Either we build a wall or we open the borders and let everyone in,” is an argument that was put forth to justify a very expensive wall between the U.S. and Mexico. The truth was that choosing not to build the wall wouldn’t end the need to continue enforcing the border policies. An ad hominem attack uses faulty logic to discredit someone. “He isn’t fit to run for president because he’s been hospitalized for depression” presupposes that someone who has been ill is not fit to hold office. May many more learn about fallacies which shine light on faulty logic.