Look up 1 Timothy 3:10, Revelations 2:15, and 2 John 1:9-10. If there can be good doctrine, then there can also be bad doctrine. We need to know our Bible well enough to be able to tell if the doctrine that someone is talking about is good or bad.
Look up Ephesians 4 paying special attention to verse 14. Doctrine could be defined as Scriptural truths from God’s Word. When Jesus spoke, He gave doctrine. He didn’t speak to tell jokes, stories, to party, or to entertain who He was speaking to. He taught doctrine. Look up Matthew 7:28, 22:3; Mark 1:22, 27, 4:2; and Luke 4:32.
Hebrews 10:22 “Let us draw near with a true heart in full assurance of faith, having our hearts sprinkled from an evil conscience, and our bodies washed with pure water.” The sixth kind of conscience that we can have is an evil conscience. This kind of conscience is knowingly and willfully wrong and is doing wrong to either yourself or others. If this is our conscience, we need to repent and live right.
1 Timothy 4:2b “having their conscience seared with a hot iron;” If you will take the time to read the surrounding verses for context, it is talking about how in the last days before the rapture people are going to depart from the faith, in part by having a seared conscience. That seared conscience may come from something that happened in the past quickly and suddenly, or it may come from a slow build of hurts or trials. Regardless, it needs to be worked on to have a pure conscience again.
Titus 1:15 “Unto the pure all things are pure: but unto them that are defiled and unbelieving is nothing pure; but even their mind and conscience is defiled.” The fourth kind of conscience that we can have is a defiled or corrupted conscience. Whether we polluted our conscience ourselves or someone else did, we need to work on correcting that type of conscience. Many times correcting it will start with either forgiving ourselves and/or someone else. After forgiveness, we can work on changing the way we think and ultimately have a pure conscience.