Verbal arguments: assumptions, alternative causes and evidence direction
| English | Français |
|---|---|
| self-selection/self sɪˈlekʃn/ | self-selection |
| necessary assumption/ˈnesɪsəri əˈsʌmpʃn/ | necessary assumption |
A decision before an answer
- If an argument needs two groups to be comparable, evidence that they differed before treatment can weaken its causal conclusion.
- Your goal: Separate observations, assumptions and conclusions.
Read the relationship
- Translate a short argument into evidence, conclusion and missing bridge. An assumption is what the reasoning needs but has not established. Avoid searching for a sentence that merely sounds reasonable or morally desirable. The target is the inference from these premises to this conclusion.
- Choose evidence that strengthens or weakens the precise argument.
Which most weakens the workshop argument?
Baseline differences provide an alternative explanation.
Use the defining rule
- For a causal claim, test alternative explanations, reverse direction and relevant baseline differences. Evidence that an outcome followed a change establishes sequence; it does not isolate the change’s effect. A comparison group helps only if important conditions are sufficiently comparable or accounted for.
- Use an assumption’s negation to test whether the argument depends on it.
An increase in the group mean establishes:
Mean change does not determine each individual change or cause.
Check the conditions
- Strengthening and weakening are directional rather than absolute. A relevant new fact can make the conclusion more or less plausible without proving or refuting it. Ask how the fact changes the link: supports a missing mechanism, removes a competing cause, exposes a selection bias or shows the result under opposite conditions.
- Use an assumption’s negation to test whether the argument depends on it.
Original argument: “Students who chose the optional revision workshop scored higher than those who did not. Therefore the workshop caused the higher scores.” Missing bridge: self-selection did not adequately explain the difference. If workshop attendees were already scoring higher before it began, the conclusion weakens. If comparable students were randomly allocated and only attendance differed, the causal inference strengthens. Neither the workshop’s popularity nor its colourful materials isolates an effect. For “every attendee improved,” an average group increase alone is insufficient because individual outcomes can differ.
A claim that an intervention produced the outcome is a ____ claim.
It asserts an effect, beyond temporal association.
Apply the task format
- For a necessary-assumption task, negate a candidate carefully and ask whether the stated argument loses its support. This technique identifies dependence, not universal truth. Some options are sufficient for a conclusion but stronger than necessary. Keep claim scope precise: average improvement differs from every participant improving.
- Use an assumption’s negation to test whether the argument depends on it.
A fact can be relevant to the topic without affecting the inference. Identify the mechanism by which it changes support.
Which answer fits this case?
Separate observations, assumptions and conclusions
Evidence must prove a conclusion completely to strengthen it.
Strengthening can increase support without proof.
Keep the distinctions
- self-selection 自我选择 — People’s choice of a group that may create relevant baseline differences.
- necessary assumption 必要假设 — A premise whose failure undermines the given reasoning.
- Separate observations, assumptions and conclusions.
- Choose evidence that strengthens or weakens the precise argument.
- Use an assumption’s negation to test whether the argument depends on it.
Match each term with its precise meaning in this lesson.
Keep the distinctions stated in the teaching example.
Put this lesson’s reasoning or event sequence in order.
The order follows the stated process; check each stage before the next.