“You have heard that it was said to those of old, ‘You shall not commit adultery. But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart. If your right eye causes you to sin, pluck it out and cast it from you; for it is more profitable for you that one of your members perish, than for your whole body to be cast into hell. And if your right hand causes you to sin, cut it off and cast it from you; for it is more profitable for you that one of your members perish, than for your whole body to be cast into hell.”
[Note: this post is a thought experiment. The arguments made in this post should not be considered advocacy.]
Christ’s condemnation of lust in this context is predicated on its pathology, in that it leads to adultery. He does not say that it was sinful to lust after a woman, save insofar as it was covetous to do so. Furthermore, his prescriptive remedy is conditional (“if your right eye causes you to sin…”), which implies that it is not the looking that is sinful, though it can result in sin. Thus, his disciples should guard against lust because of where it can lead.
Not only that, he specifically targets adultery as the reason to avoid lust, and not the more general term “fornication.” Since adultery implies that at least one of the participants is married, there is the potential for covetousness in the act of lust. If the one doing the lusting is married, then one’s lust is definitely covetous since the object of one’s lust cannot rightfully belong to the one doing the lusting. Conversely, if the one doing the lusting is lusting after one who is married, then this also conveys an element of covetousness since the object of one’s lust does cannot rightfully belong to the one doing the lusting.
That aside, the broader issue regarding pornography is the matter at hand. Since lust is not condemned as inherently sinful (only as leading to sin), the question then becomes: would lust be sinful if it could not lead to sin? For example, if one were to lust after the images of a dead porn star, would this be wrong since there is no way that the one doing the lusting could ever commit adultery with the object of one’s lust? Additionally, if there is no practical way to act on lust (i.e. one would never have access to the object of one’s lust), can lust be considered sinful since there is no way to act on it?
Some might object to lust on the general grounds that it leads to an increased tendency to commit adultery in general. This objection is not particularly relevant, though, since Christ makes it clear that lust after a specific woman leads to committing adultery with that specific woman in one’s heart. While general lust might be condemned under the auspices of leading to a general tendency to commit adultery, specific lust should not be condemned for leading to a general tendency to commit adultery because that pathology does not necessarily follow.
When all is considered, citing Matthew 5 to condemn pornography is not an air-tight argument since Christ’s condemnation of lusting after a woman is predicated on its specific pathology. It is thus tricky to base a general condemnation on a specific claim. However, there are plenty of good arguments against pornography, particularly those that are based on a theological perspective derived from nature or a theological perspective based on ideal relationships. Thus, it might be better to base an argument against pornography on a more theologically sound argument instead of trying to find things in God’s word that aren’t actually there.