Identifying Logical Fallacies Flashcards

A patient with chronic migraines decides to eliminate gluten from their diet. Two weeks later, they report having fewer migraines and conclude that the gluten-free diet is the definitive cause of their improvement. Which logical fallacy is most evident in the patient's conclusion?

Answer: Post Hoc Ergo Propter Hoc (False Cause)

The patient is committing the Post Hoc Ergo Propter Hoc (meaning 'after this, therefore because of this') fallacy by assuming that because the improvement in migraines occurred after they started the new diet, the diet must have been the cause. [2, 6, 12] This conclusion ignores other potential contributing factors, such as a placebo effect, other lifestyle changes, or the natural waxing and waning of the condition.

During a team meeting to update patient care protocols, a senior nurse objects to a new, evidence-based method for IV insertion. The nurse argues, 'We shouldn't change our method. The way we've been doing it for the past 20 years has always been good enough for our patients.' This reasoning is a classic example of which fallacy?

Answer: Appeal to Tradition

The nurse's argument is based on the premise that the old method is superior simply because it is long-standing. This is an Appeal to Tradition fallacy, which resists change by citing historical preference ('we've always done it this way') rather than current evidence or a comparison of effectiveness. [7, 8, 21, 27]

A physical therapist treats a 22-year-old elite athlete who recovers from a specific knee surgery in just four weeks. Based on this single case, the therapist begins telling all their knee surgery patients, including a 65-year-old with osteoarthritis, that they should also expect to recover in four weeks. This is an example of which logical fallacy?

Answer: Hasty Generalization

The therapist is making a Hasty Generalization by drawing a broad conclusion about all knee surgery patients based on a very small and unrepresentative sample (a single, young, elite athlete). [19, 25, 34] This flawed reasoning ignores significant variables like age, comorbidities, and pre-surgical fitness levels that affect recovery time.

A hospital dietitian suggests to a patient with type 2 diabetes that they should try to reduce their intake of refined sugars to better manage their blood glucose levels. The patient angrily replies, 'So you're telling me I can never eat a piece of fruit or a slice of bread again? You want me to starve!' Which fallacy has the patient used in their response?

Answer: Straw Man

The patient is committing a Straw Man fallacy. They have ignored the dietitian's actual, moderate suggestion ('reduce refined sugars') and replaced it with a distorted, more extreme, and easily refutable position ('never eat fruit or bread,' 'starve') in order to attack it. [33, 36, 38]

A surgeon presents treatment options to a patient with a benign tumor, stating, 'We can either perform a highly invasive surgery that will remove the tumor completely, or we can do nothing and just let it grow.' This statement is a potential example of which logical fallacy if other viable options exist?

Answer: False Dichotomy (Either/Or)

This is a False Dichotomy because the surgeon presents only two extreme options (major surgery or nothing) while ignoring other potential intermediate options. [26, 32, 35] Viable alternatives might include minimally invasive procedures, targeted radiation, or a 'watchful waiting' approach with regular monitoring. The fallacy lies in artificially limiting the choices to only two.

At a medical conference, a young cardiologist presents compelling research data that challenges a long-held belief about a particular medication. During the Q&A, a senior physician dismisses the findings by saying, 'This research comes from a junior fellow at a small community hospital. I doubt they have the resources or experience to produce a truly valid study.' This comment is an example of which logical fallacy?

Answer: Ad Hominem

The senior physician is committing an Ad Hominem fallacy. Instead of addressing the merits, methodology, or data of the research presented, the physician is attacking the character and circumstances (junior status, small hospital) of the person presenting it. [1, 5, 10] The argument is directed at the researcher, not the research itself.