We will say anything to excuse our immoral behavior. Why? We do so in order to ease our conscience.
In John 12:18 Jesus prays amongst a crowd of onlookers, "Father, glorify Your name." Then a voice came out of heaven: "I have both glorified it, and will glorify it again." So the crowd of people who stood by and heard it were saying that it had thundered; others were saying, "An angel has spoken to Him."
They excused the voice from heaven in order justify their disbelief in Christ and His will. Hence, the power of the conscience.
O how I'm reminded of the times we have justified our immoral behavior by disregarding the clear voice and will of God. Otherwise our conscience would be burdened.
Someone may justify fornication by responding that the Bible never teaches that we shalt not have sex outside of marriage. So we show them a teaching of Paul clearly condemning fornication.
Then they will respond that Jesus never mentions fornication. So we show them Christ's words condemning fornication.
Then they will respond that the Bible could never be inspired and inerrant since modernity has proven away the miraculous. Why argue with this person any longer? Not even the voice of God could change their mind. (See passage above.)
We will say anything to excuse our behavior, thus showing the power of the conscience.
Prayer: LORD, show me where I have excused sin in my life so that my conscience would remain unburdened. Give me the power to overcome this sin. Then allow me to experience the freedom of a truly guiltless conscience.