# by the hypocrisy of liars

"They will learn these things by the hypocrisy of liars" 

# their own consciences having been seared

Possible meanings are 1) Paul is speaking of people who can no longer tell that they are doing wrong as if their minds were skin that someone had burned with a hot iron. or 2) Paul is speaking of these people as if Satan had put a mark on them with a hot iron to indicate that they belong to him.