A woman’s place is in the bosom of her family; her thoughts ought seldom to emerge from it.

The Edinburgh Magazine and Literary Miscellany, Volume 97, 1825

Those nineteenth-century moralists! Can you imagine what today’s world would have been like if women such as Florence Nightingale, Emmeline Pankhurst, or Harriet Beecher Stowe had confined their thoughts to family life? While the viewpoint behind it may be outdated, this famous quotation is a neat way of illustrating one of the main uses of ought, namely expressing the speaker’s view as to a correct or dutiful course of action, often imbued with a tinge of social rectitude.

As you may know, ought is a special type of verb known as a modal verb: I’ve covered some of these already in earlier blogs. I’d now like to turn my attention to a trio of modals which share a similar range of meanings: must,ought, and should. All these verbs can be used to talk about duty and obligation, to give advice or instructions, or to express degrees of probability.Should can also be used in other ways, but as I’m endeavouring to keep this fairly brief, I’ll save my discussion of conditional meanings of should and the difference between should and would for another day. If you’re avid for all the gen right this minute, you can find a full rundown of should here.

Let’s explore the central meanings of must, should, and ought first, then we’ll turn to their similarities and differences, so as to help you use each verb in the most effective and idiomatic way.

MUST

We use must in three main ways:

• to talk about something that has to be done because it’s compulsory or obligatory (that is, it’s absolutely necessary to obey a rule, law, order, or instruction):

Online stores must give a cooling-off period of seven working days.
She was told that she must not discuss the case with third parties, including her MP.

or because it’s very important:

To calm public opinion, police must quickly arrest the culprits and solve this case.
I must get back to work: a deadline approaches.

• to express the view that something is highly likely because it’s a logical conclusion based on something else that the speaker knows, or it’s the normal…

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