Identifying Assumptions

Assumptions are the hidden premises of an argument — beliefs that the author takes for granted without explicitly stating them. They are the glue that holds premises and conclusions together, and they are among the most commonly tested elements in LNAT Section A. If you can reliably identify assumptions, you can answer not only assumption questions but also strengthening, weakening, and flaw questions with confidence.

---

What Is an Assumption?

An assumption is an unstated belief that must be true for the argument to work. The author does not argue for the assumption — they simply take it for granted.

Formal Definition: An assumption is a claim that is not explicitly stated in the argument but is necessary for the conclusion to follow from the premises.

How Assumptions Relate to Other Components

Component	Stated?	Supported?	Necessary for the argument?
Premise	Yes — explicitly stated	Often (with evidence)	Yes
Conclusion	Yes — explicitly stated	By the premises	Yes
Assumption	No — unstated	No — taken for granted	Yes

Key Insight: Every argument contains assumptions. This is not a flaw — it is unavoidable. Even the most rigorous argument cannot state every belief it relies on. The LNAT tests whether you can identify the most important unstated beliefs.

---

Where Assumptions Hide

Assumptions lurk in the logical gap between premises and conclusion. Whenever you see a premise and a conclusion that are not perfectly connected by explicit reasoning, there is an assumption bridging the gap.

The Gap Model

Premise: "Rehabilitation programmes reduce reoffending."
                    ↓
              [ASSUMPTION GAP]
                    ↓
Conclusion: "The government should fund more rehabilitation programmes."

What is the assumption? The argument assumes that reducing reoffending is a goal the government should pursue and that funding rehabilitation is the best (or a good) way to achieve it. Neither of these is stated.

Finding the Gap

To find assumptions, look for the logical distance between premises and conclusion:

1. Read the premise(s) carefully
2. Read the conclusion carefully
3. Ask: "What must be true — but is not stated — for this conclusion to follow from these premises?"

---

Types of Assumptions

1. Bridging Assumptions

These connect the premises to the conclusion by linking a concept in the premises to a concept in the conclusion.

Premise: "Social media use is correlated with higher rates of anxiety among teenagers." Conclusion: "Parents should limit their children's social media use." Bridging assumption: "Correlation indicates a causal relationship" AND "Parents can and should control their children's social media use."

The premise discusses a correlation. The conclusion recommends action. The assumptions bridge the gap between observation and recommendation.

2. Background Assumptions

These are general beliefs about the world that the argument takes for granted.

Premise: "The UK's electoral system produces disproportionate results." Conclusion: "The UK should adopt proportional representation." Background assumption: "Proportional representation produces better (more proportionate) results."

This is widely believed, but the author does not argue for it — they simply take it as given.

3. Value Assumptions

These are unstated beliefs about what is good, right, or important.

Premise: "Universal healthcare ensures that the poorest citizens receive medical treatment." Conclusion: "The government should implement universal healthcare." Value assumption: "Ensuring medical treatment for the poorest citizens is a sufficiently important goal to justify government intervention and its associated costs."

The argument relies on a value — that caring for the poorest is a priority — that the author does not explicitly defend.

4. Factual Assumptions

These are unstated beliefs about how the world works.

Premise: "Increasing the minimum wage will give low-income workers more spending power." Conclusion: "Increasing the minimum wage will reduce poverty." Factual assumption: "Increased spending power leads to reduced poverty" AND "Employers will not respond by cutting jobs (which would negate the benefit)."

---

How to Identify Assumptions: A Systematic Method

Step 1: Identify the Conclusion

What is the author arguing for? State it clearly.

Step 2: Identify the Key Premises

What reasons does the author give? List them.

Step 3: Identify the Concepts

What concepts appear in the conclusion that do not appear in the premises? What concepts appear in the premises that do not appear in the conclusion?

Step 4: Find the Bridge

The assumption connects the concepts in the premises to the concepts in the conclusion.

Worked Example