Similarly, other people cannot know our innermost secrets, although they can figure things out through natural knowledge and by deduction. For instance, I have no special occult knowledge, but it seems to me I know, just from observing behavior, when something a person does or says might be a little disingenuous. I can often tell if they have this tendency or that tendency, and on occasion, I can tell when the life they claim to be living may not be as authentic as they pretend it to be. Call it intuition or being a good judge of character, I'm convinced it is a completely natural ability many people have. I may be completely deluded too.
Observing behavior is kind of how the devil figures things out about us as well; he is able to surmise from our behaviors, our speech, our attitudes, our weaknesses, what is deeply hidden. The temptations he assaults us with can reveal a great deal about us, both to ourselves and to the devil - especially if we fall. When we fall, the devil then knows for sure, and the cycle of temptation repeats, accelerating in severity. The devil has been doing this ever since the Fall, so he has lots of experience, which is how he deceives people so easily and frequently. But don't be misled, the devil's knowledge is greater than human knowledge, and since he is an angel, he possesses supernatural knowledge.
Now for us, self-knowledge can be an important safeguard against the devil's wiles. Naturally, despite the fact we can figure things out about others, we are often unable to figure out ourselves. Even so, life experience, rising and falling through our weaknesses, indeed, all of our shortcomings usually result in a greater self-knowledge; although it is easier to enter that chamber through prayer and (the sacrament of) penance. Enduring temptations manfully is a penance. For the just man, as well as the sinner, temptations reveal what he is. That said, self-knowledge also informs and guards against inappropriate or dangerous associates and the occasion of sin.
Anyway - because we have intelligence, we can sometimes figure stuff out naturally, or even 'know' something is likely to happen - although it doesn't always mean we are right. The benefit of being mistaken serves to prove we can never know another person's motives, responsibility, or culpability - God alone knows that. The lesson learned ought to be, in part, that we should never trust in our so-called "knowledge" be it of others or our self. We must trust in God alone, and abandon ourselves to His loving providence. The other lesson is that we would be better off minding our own business as well.
However, I read a now very public story on Catholic News Agency about a well known priest who evidently had a fall from grace. I wasn't surprised... it was just a matter of time. I pray for him and for all of our priests. There is nothing else to say.
"He who dwells in the shelter of the Most High
and abides in the shade of the Almighty
says to the Lord, 'my refuge,
my stronghold in whom I trust!'
It is he who will free you from the snare
of the fowler who seeks to destroy you;
he will conceal you with his pinions
and under his wings you will find refuge." - Ps. 90