Hi, everyone. I'm Jade. What we're talking about today is using modal verbs to make deductions
about a situation. But first, I need to tell you what does it mean to make a deduction.
Well, let's imagine there's a situation. You see something, you observe something. This
is your evidence. "John looks tired." This is what you see. This is your evidence. Your
deduction is how you interpret what you see. Your deduction is what you say about what
So, for example, these are all different deductions you can make. You can say, "He must be unwell."
When we're making deductions about the present, things that are true now, in this moment,
we use this structure. We use modal verb plus bare infinitive. So, in the first example,
this is the modal verb, and then this is the bare infinitive. It will always take this
structure to make a deduction about the present. So, when we say, "He must be unwell", "must"
carries the meaning of certainty. So, I see John, I see he's tired, and I interpret that
as certainty. I understand the situation fully, and I'm saying that he's tired. I could, however,
say, "He might not be sleeping well." In this case, I'm using a different modal verb. I'm
using "might". "Might" is my modal verb. And also, this one's a negative. So, the negative
goes in the middle position. The negative goes after the modal verb. Too many pens going
on here now. So, the negative goes in between the two verbs. "He might not be sleeping well."
"Might" is not as certain as "must". "Might" here means possibility. I'm looking at him,
I see he's tired. My thought about the situation… My thought about the situation is that it's
possible that John's tired. He might not be sleeping well. Here's another variation. "He
may be stressed." Again, this means possibility. What's the difference between "might" and
"may"? In British English, "may" is a little bit… Slightly more formal. That's the difference.
And then, what about this one? "He can't be feeling well." When we use "can't" to make
a deduction… Sorry, we always have to use it in the negative. We can't… We can't do
it. "He can be", it doesn't make sense as a deduction. It always has to be "can't".
So we can say, "He can't be feeling well." And this one, again, is certainty. So we could…
If we're certain about our deductions, we would either use "must" or "can't" to do that.
So it's not too hard. What if we're not talking about deductions about the present, ones that
are true now? What if we're talking about past events? Hmm, what do we do then? Well,
we use a different grammar structure. We use modal verb plus "have" plus the past perfect.
So I find it easy in that when we see "have" there, it shows us that we're talking about
something in the past. That's what you need to remember. "Have" shows us we're talking
about the past. Let's look at some examples. Here's a different observation. "Mr. Smith
didn't attend today's meeting." Full stop. So what we see and experience, we go to the
meeting… Well, I'm going to say I go to the meeting. I go to the meeting, I expected
to see Mr. Smith there, he was not there. That is my evidence, that's my observation.
So what kind of deduction do I make following that? "He must have forgotten about it. I
know Mr. Smith, I know he's forgetful, therefore my deduction is he must have forgotten." Here's
the structure, modal verb, then followed by "have", followed by the past participle. This
verb is "forget", the past participle is "forgotten". What does it mean? If we're using "must",
it's the same. "Must" means certainty. You're quite sure. You know him well and you're quite
sure that he's forgotten about this… He forgot the meeting. Because again, we're talking
What about this one? "He might have missed his train." To reflect possibility. You're
not quite certain about it this time. You know Mr. Smith, he's generally a reliable
guy, so you think that, you know, it must have been something outside of his control.
It's possible that he didn't come to the meeting because he didn't manage to get his train
Next example, "He may have called in sick." What does it mean to call in sick? That means
when you're not feeling well, so you call up your job and you say, "Oh, I'm not coming
today." That's what it means to call in sick. Again, we have exactly the same difference.
"May" is slightly more formal than "might". "He may have called in sick." I'm not sure,
it's like a suggestion, it's a possibility.
And finally, "He can't have known about it." You know Mr. Smith well, you know that whatever
he would do, he would do anything to come to this meeting. The only way that can explain
the reason he's not here is if he didn't know about this meeting for some reason. To reflect
certainty, we're using "can't". And because we're talking about the past, again, we're
using "have" and then past participle. So, that's how you do it. If you have a situation
and you need to make a deduction on that situation, here's your observation, here's your evidence,
but then you need to say something about it, give an opinion. What you need to do is be
using these grammar structures. For talking about the present, there's no "have" in there,
but for talking about a past event, then we use "have" in there to make our deduction.
What you need to do now is go to the engVid website where you can do the quiz on this.
Flex your grammar muscles doing the quiz. And what I'd also like you to do before you
go there is subscribe here on my engVid channel. Yeah, and come again and watch more videos
from me. So, I'm going to go and flex more of my grammar muscles, and you're going to