Introduction: The "Missing Piece" of the Puzzle

Have you ever listened to someone make a point and thought, "Wait, there is a step missing there"? In Thinking Skills, that "missing step" is often an unstated assumption. Understanding assumptions is like being a detective; you are looking for the hidden ideas that an author believes to be true but hasn't actually written down on the page.

Mastering this skill is vital for Paper 2 (Critical Thinking). It helps you see how arguments are really built and prepares you to evaluate whether those arguments actually hold water.

What exactly is an Unstated Assumption?

In the context of an argument, an unstated assumption is a bridge. It is a claim that the author must believe to be true in order for their reasons to support their conclusion, but they have not explicitly stated it.

Think of an argument like a physical bridge:

1. The Reasons are one side of the river.
2. The Conclusion is the other side.
3. The Assumption is the invisible structure underneath that allows you to walk from the reasons to the conclusion.

Important Distinction: If it is written in the text, it is a reason. If it is not written in the text but is necessary for the argument to work, it is an unstated assumption.

Note: To review the parts of an argument that ARE stated (like intermediate conclusions or counter-arguments), see the chapter "Identify key elements of an argument and explain their function."

How to Identify an Assumption: The "Gap" Method

To find an assumption, you need to look for the "gap" between the reason and the conclusion. Ask yourself: "What else would have to be true for this reason to lead me to this conclusion?"

Example:
"The school cafeteria has started serving spinach every day. Therefore, the students will become much healthier."

The Reason: Spinach is served every day.
The Conclusion: Students will become healthier.

The Gap: Is there something missing? Just because spinach is served doesn't mean students are eating it!
The Unstated Assumption: The students will actually eat the spinach.

The "Negative Test" (The Secret Weapon)

If you aren't sure if something is a necessary assumption, try the Negative Test (sometimes called the Reversal Test). Simply pretend the assumption is false. If the argument falls apart and the conclusion no longer makes sense, then you have found a genuine unstated assumption.

Let's try it with the spinach example:
Assumption: Students will eat the spinach.
Make it negative: Students will NOT eat the spinach.
Result: If they don't eat it, they won't get healthier. The argument collapses! This proves "Students will eat the spinach" is a necessary unstated assumption.

Syllabus Rules: What is NOT an Assumption?

The Cambridge 9694 syllabus is very specific about what counts as an assumption in your exam. Don't worry if this seems tricky at first; just remember these three "No-Go" zones:

  1. No Speculation about the Author: Do not guess what the author is thinking personally or what their motives are (e.g., "The author probably hates junk food").
  2. No Speculation about the Situation: Do not imagine extra facts outside the argument (e.g., "Maybe the students are allergic to spinach").
  3. No Speculation about the Reader: Do not guess how the reader might react to the argument.

Key Rule: An assumption must be a logical necessity for the argument to function, not just a random "maybe."

Common Types of Assumptions

While every argument is different, assumptions often fall into these patterns:

1. The "Similarity" Assumption: Assuming that because two things are alike in one way, they are alike in another. (e.g., "It worked in London, so it will work in Tokyo." Assumption: London and Tokyo are similar enough for this specific plan to work.)

2. The "Better/Worse" Assumption: Assuming that a certain outcome is actually desirable. (e.g., "We should increase taxes to build a new stadium." Assumption: A new stadium is more important than the money lost through taxes.)

3. The "Cause and Effect" Assumption: Assuming that because one thing happened after another, the first thing caused the second. (Assumption: There is no other factor causing the change.)

Step-by-Step Guide for the Exam

When you are asked to "identify an unstated assumption" in Paper 2, follow these steps:

Step 1: Identify the Main Conclusion. What is the author trying to prove?
Step 2: Identify the Reasons given for that conclusion.
Step 3: Look for a jump in logic. Is there a word or idea in the conclusion that wasn't in the reasons?
Step 4: Formulate a simple statement that bridges that jump.
Step 5: Apply the Negative Test to double-check.

Quick Review: Key Takeaways

1. Hidden, not Written: If it's in the text, it's not an assumption.
2. Necessary: The argument must need the assumption to be true to work.
3. Use the Negative Test: If the "flipped" version kills the argument, you've found it!
4. Stay Focused: Avoid speculating about the author's feelings or external "what-ifs."

"Don't forget: an assumption is the 'silence' in the argument that speaks the loudest!"