Identifying Premises and Evidence

Having learned to identify conclusions, you now need to master the other half of argument structure: premises and evidence. Premises are the reasons an author offers to support their conclusion. On the LNAT, you will frequently be asked which statements support the author's argument, what evidence is provided, and whether the evidence is sufficient.

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Premise Indicator Words

Just as conclusions have indicator words, premises are often signalled by specific words and phrases:

Indicator	Example
Because	"Tuition fees should be reduced because they deter low-income students."
Since	"Since crime rates have fallen, the policy must be working."
Given that	"Given that resources are limited, priorities must be set."
As	"As the population ages, healthcare demand will increase."
For	"The plan should be rejected, for it fails to address the root cause."
The reason is that	"The reason is that existing regulations are inadequate."
Due to the fact that	"Due to the fact that emissions continue to rise, action is urgent."
On the grounds that	"The appeal was dismissed on the grounds that no new evidence was presented."

Important: Like conclusion indicators, premise indicators are helpful but not always present. Many premises are stated without any indicator word at all.

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Types of Evidence

Not all premises are created equal. The LNAT tests your ability to recognise different types of evidence and evaluate their strength.

Empirical Evidence

Evidence based on observation, experiment, or data collection.

"A randomised controlled trial involving 5,000 participants found that the drug reduced symptoms by 40%."

This is strong evidence because it is based on a rigorous, large-scale study.

Statistical Evidence

Evidence presented in numerical form — percentages, averages, rates.

"78% of teachers surveyed reported that class sizes had increased over the past five years."

Statistical evidence can be persuasive but must be evaluated carefully (Who was surveyed? How large was the sample? Was the question leading?).

Anecdotal Evidence

Evidence based on individual cases or personal experience.

"My neighbour was burgled last week, which shows that crime is getting worse."

Anecdotal evidence is the weakest form — a single case cannot establish a general trend.

Expert Testimony

Evidence based on the opinion of a recognised authority.

"Leading climate scientists agree that global temperatures will rise by at least 1.5°C by 2050."

Expert testimony is strong when the experts are relevant and there is genuine consensus, but it can be misused (appeal to authority fallacy).

Analogical Evidence

Evidence drawn from comparison with a similar case.

"The policy worked in Sweden, so it should work in the UK."

Analogical evidence depends on whether the two cases are sufficiently similar in relevant respects.

Type	Strength	LNAT Relevance
Empirical	Strong (if well-designed)	Often presented in passages; test asks if it supports the conclusion
Statistical	Moderate to strong	Frequently tested; look for misleading use of statistics
Anecdotal	Weak	Often a distractor or flaw in reasoning
Expert	Moderate to strong	Test may ask whether the appeal to expertise is justified
Analogical	Variable	Test frequently asks whether the analogy is valid

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Distinguishing Evidence from Assertion

A critical skill on the LNAT is distinguishing between a statement that provides evidence and a statement that is merely an assertion (a claim made without supporting evidence).

Evidence

"A 2023 study by the Institute for Fiscal Studies found that graduates from disadvantaged backgrounds earn 10% less than their peers five years after graduation."

This is evidence — it cites a specific source and specific data.

Assertion

"The university system fails disadvantaged students."

This is an assertion — a claim made without any evidence to back it up. It might be true, but it is not supported in this statement.