Obligations, Commands, and Advice
3.6 ⚠️ Obligations, Commands, and Advice
Learn how to manage duties, strict rules, and recommendations using Must, Should, and Ought to.
🗺️ Necessity Spectrum
[ WEAK ADVICE ] ─────────────────────────────────────────► [ STRICT REQUIREMENT ]
Ought to / Should Must / Have to
“It is a good idea.” “It is mandatory by law.”
📊 Force Level Matrix
| Modal Verb | Force Level | Meaning | Example |
|---|---|---|---|
| Should | Soft / Medium | Good advice or recommendation | You should sleep early before the exam. |
| Ought to | Soft / Medium | Moral duty or expectation | We ought to help our new neighbors. |
| Must | Strong / Maximum | Absolute rule or law | Drivers must stop at the red light. |
| Must not | Prohibitive | Forbidden / Illegal action | You must not share confidential data. |
📝 Real-World Examples Explained
1. Strict Legal Requirement
“All visitors must sign their names at the security desk.”
- must: Non-negotiable safety rule.
2. Helpful Work Advice
“You should proofread your email before sending it to the director.”
- should: Helpful advice; recommended professional practice.
3. Moral Duty
“We ought to support small local businesses during tough times.”
- ought to: Expresses what is right or morally expected.
🚫 Common Mistakes: Correct vs. Incorrect
1. Using “Must” When Giving Casual Advice
❌ Incorrect: “You must try the chocolate cake at this cafe!” (In formal writing)
✅ Correct: “You should try the chocolate cake at this cafe!”
Why it’s wrong: Using must for casual suggestions sounds overly demanding in formal writing. Use should.
2. Confusing “Must Not” with “Don’t Have To”
❌ Incorrect: “You must not come to work on Sunday because the office is closed.”
✅ Correct: “You don’t have to come to work on Sunday.”
Why it’s wrong: Must not means forbidden/illegal. Don’t have to means optional.
✏️ Quick Quiz: Must or Should?
Fill in the blanks:
- “Employees ________ wear safety goggles inside the chemical lab.” (Strict law)
- “You ________ drink more water during hot days.” (Good advice)
🔑 Quiz Answers
- Question 1: must
- Question 2: should