Critical Thinking: MDCAT Logical Reasoning notes
Critical Thinking MDCAT notes: reading only what a passage states, fact vs inference, moral vs practical arguments, hypothesis vs theory, examples.
What critical thinking questions test
These questions check whether you can reason only from the information given, separate facts from assumptions, and judge the kind of argument being made. Your general knowledge is not the test; the passage or statement is.
Skill 1: stated, implied or unsupported
For each statement about a passage, ask three questions:
- Is it directly stated? Then it is correct.
- Does it necessarily follow from what is stated? Then it is a valid inference.
- Does it add something the passage never says (a cause, a method, a future result, words like "by force", "always", "ultimately")? Then it is unsupported, even if it seems plausible.
Worked example
Passage: "Penicillin was discovered in 1928. Its large-scale production began during the Second World War."
- I. Penicillin was discovered before the Second World War. Follows (1928 is before the war began).
- II. Penicillin saved millions of soldiers. Does not follow (not stated).
- III. Penicillin was discovered by accident. Does not follow (true historically, but not in the passage).
Answer: only I.
Skill 2: types of argument
| Type | Based on | Example |
|---|---|---|
| Moral (ethical) | Right and wrong, rights, consent, fairness | It is wrong to use patients' records without their consent. |
| Practical / economic | Profit, cost, efficiency, competition | Using the records will cut costs. |
| Legal | What the law requires or forbids | The law bans sharing records. |
| Consequential | Likely results | Patients may stop trusting the hospital. |
A moral argument uses words like wrong, right, fair, duty, consent. An argument about lost trust hurting profits is practical, not moral.
Skill 3: scientific terms
- Hypothesis: a tentative, testable explanation or prediction.
- Theory: a well-substantiated explanation supported by repeated testing and a large body of evidence.
- Law: a description (often mathematical) of what always happens under given conditions.
- Fact / observation: something directly measured or seen.
Skill 4: essential association
Some items ask which word is always (necessarily) associated with another. Choose the element without which the thing cannot exist, not one that merely often goes with it.
- A signature (autograph) cannot exist without a writing instrument; it can exist without a singer or actor.
- A shoe always has a sole; it does not always have laces.
- A book always has pages; pictures are optional.
Skill 5: evaluating arguments
- Assumption: an unstated idea the argument needs to be true.
- Strengthen: new evidence that makes the conclusion more likely.
- Weaken: evidence that breaks the link between premise and conclusion.
- Correlation is not causation: two things occurring together need not mean one causes the other.
Common MDCAT traps
- Adding outside knowledge: a true fact that is not in the passage still "does not follow".
- Extreme words (all, always, by force, ultimately) usually go beyond the passage.
- Confusing a consequence-based or profit-based argument with a moral one.
- Thinking a theory is "unproven": in science a theory is strongly supported.
Quick revision
- Answer only from the given information.
- Moral arguments are about right and wrong.
- Hypothesis is tentative; theory is well tested.
- "Always associated" means essential, not common.
- Look out for unstated assumptions.