The vast majority of all that we see we see correctly. Even in the first few minutes out of bed in the morning, we have already had hundreds of correct perceptions: the sun is shining, these are my socks, breakfast smells good.

Correct perceptions are strong. Once we see something with a correct perception, we can truly say that thing exists.

These correct perceptions come in three types. Most of them are the direct type. I see a color, I hear a sound, I smell or taste or touch something. Hearing our thoughts in our own minds is also a direct type of correct perception.

Deduction is another kind of correct perception: I may not be able to see my socks on the floor in the morning, if they're covered by my pants. But if I dropped them there last night and I've had no visitors in the meantime, I know the socks are there, as surely as if I see them.

The last kind of correct perception is based on authority: I'm in my bedroom and can't see the kitchen, but Mother tells me there's still some breakfast left. And I know it's there, because she's a truthful person.