In a world under the sway of the wicked one (1st John 5:19), in which little regard is paid to chastity, few understand the distinction between various forms of sensuality.

Lust is a sin of the eyes, and occurs within the imagination. Jesus warned, “Whoever looks at a woman to lust for her has already committed adultery with her in his heart” (Matthew 5:28). Fantasizing about sexual encounters with a person other than one’s own spouse is expressly forbidden. What is casually called “undressing her with your eyes” is more accurately understood to be “raping her with your heart”. Job was determined to keep his mind pure, insisting, “I have made a covenant with my eyes; Why then should I look upon a young woman?” (Job 31:1). Looking may seem harmless, but “The lamp of the body is the eye. Therefore, when your eye is good, your whole body also is full of light. But when your eye is bad, your body also is full of darkness” (Luke 11:34).

Lewdness is a sin of the hands and body. Translated variously as “licentiousness” (NAS), “lasciviousness” (ASV, KJV), “sensuality” (ESV) or “wantonness” (ASV, KJV), Thayer defines “lewdness” (NIV, NKJV) as “indecent bodily movements, unchaste handling of males and females”. “Lewdness” is condemned by the apostles as something more than “lust” (Romans 13:13; 1st Peter 4:3), but not the same as “adultery” or “fornication” (1st Corinthians 12:21; Galatians 5:19). It is fondling, groping, “feeling her up”, getting to “second base”, pretty much what happens whenever couples are together on a dance floor, and Christ includes it among a list of “evil things” that “defile a man” (Mark 7:21-23).

Fornication is a sin of the reproductive organs. It is, according to Thayer, “illicit sexual intercourse in general”, and is translated in many versions as “sexual immorality” (ESV, NAS, NIV, NKJV). Basically, “fornication” (ASV, KJV) is the act of copulation without the divine approval of marriage (Hebrews 13:4). It is a broad category, addressing all unauthorized coitus, inclusive of bestiality (Exodus 22:19), homosexuality (Romans 1:26-27), adultery (Luke 18:20), and simple premarital sex (1st Corinthians 7:2). “This is the will of God, your sanctification: that you should abstain from sexual immorality; that each of you should know how to possess his own vessel in sanctification and honor” (1st Thessalonians 4:3-4). God wills that each person should learn self-control in order to practice abstinence, and, more than that, just run away from this wicked behavior: “Flee sexual immorality. Every sin that a man does is outside the body, but he who commits sexual immorality sins against his own body” (1st Corinthians 6:18).

Adultery is a specific manifestation of fornication involving at least one person who is bound by God to another. Thayer says it is to “have unlawful intercourse with another’s wife”. To the surprise of many, this transgression is often practiced by people who are married to one another. The Lord explained, “Whoever divorces his wife and marries another commits adultery; and whoever marries her who is divorced from her husband commits adultery” (Luke 16:18; cf. Matthew 5:31-32; 19:3-12; Mark 10:11-12). Furthermore, Paul wrote, “if, while her husband lives, she marries another man, she will be called an adulteress” (Romans 7:3). It is entirely possible to be “married” to someone else’s “wife” (Mark 6:17-18). There are grave consequences attending adultery (1st Corinthians 6:9-10) insomuch as “adultery” is a “work of the flesh” and “those who practice such things will not inherit the kingdom of God” (Galatians 5:19-21).

“Do you not know that your body is the temple of the Holy Spirit who is in you, whom you have from God, and you are not your own? For you were bought at a price; therefore glorify God in your body and in your spirit, which are God's” (1st Corinthians 6:19-20).