A Christian man studies the Scriptures and he finds that lust is not mere sexual desire or even sexual fantasy, but it is the desire to entice someone into committing fornication or adultery. He further studies and learns the Scriptural principle that we as Christians do not have to agree with the way something was made (like images of porn constructed by using unmarried actors) to enjoy the use of that thing. And he understands that he can take the good from porn (beautiful images of men and women having sex) and separate that from the bad (sinful set up stories before the sex).