1. Deduction and Probability
Aquilina Yunita, S.Pd

2. Deduction and Probability
There is a house nearby Pondok Indah Mall.
It must be true.
There is a woman named Mary lives at the house.
It can be true.
She’s killed by her own husband on Monday night.
It might be true.
She is seen hanging on the tree in front of her house since then.
It can’t be true.

3. Modals of deduction
Modals affect the meaning of sentences. For instance, some of them can be used to say how sure we are about something (probability).

4. Read these two sentences
I meet my boss at ten o'clock every day.
(a statement of fact) 
I might see my boss tonight.
(the modal 'might' expresses a probability or possibility)

5. Modal deduction – PRESENT
MUST
We use must when we feel sure that something is true because it has a strong evidence.

6. Modal deduction – PRESENT
2. Might, may, could We use these modals when we say that something is possible but we are not sure.

7. Modal deduction – PRESENT
3. CAN’T We use can’t when we feel sure something is not true.

8. Modal deduction - PAST
We can also use modal verbs to speculate about past.
Perfect Infinitive  HAVE + PAST PARTICIPLE
When we use modal verbs to talk about the past they are followed by a perfect infinitive.
Example: Must + perfect infinitive
The thieves must have come in through the window. Look! It’s still open.