Someone drives in a car and sees a dog, he keeps on driving passing the dog and then says
I think he had a collar
Why not saying the following sentence?
I think he has a collar
Someone drives in a car and sees a dog, he keeps on driving passing the dog and then says
I think he had a collar
Why not saying the following sentence?
I think he has a collar
It is past tense.
"I think he had a collar (on him, when I saw him in the past)."
I think he has a collar is present tense, implying the dog still has a collar on. However, the driver has no way to see this at the present time, so it is more reasonable to state what the driver is more certain of - the dog had a collar when seen, not now.
What is more impressive is that when driving past the dog, the driver is unsure of whether the dog had a collar, but has no doubt about its sex!