I remember Jesus explaining how anyone who even LOOKS at another lustfully,
is guilty of committing adultery in his heart. yikes.
There is intention also, at least in Matthew 5 in the sermon on the mount. He who looks at a woman
in order to lust after her has committed adultery with her already in his heart. The Greek word 'pros' is there.
The word for 'lust' has to do with coveting. We can see this in how the Hebrew was used in the Greek Septuagint that was in use at the time. I know nothing about the wording that requires _intention_ when it comes to coveting, but many or most sins to require some sort of decision. Paul warned against yielding ones members to sin.
Why do I mention this? At least in the case of attraction and sexual desire, young people... or I can say young men because I used to be one... may often feel attracted to members of the opposite sex. Many men have to desire to look more if they see a pretty girl. If a beautiful woman in a bikini falls through the roof into a man's field of vision of a Christian young man and he is attracted to her and finds her appealing when he sees her, that does not mean he sinned. (Let's say the woman lands on pillows and is completely unharmed.) If he looks at her with intention to lust, then sin becomes an issue.
And is lust purely sexual? The command is 'thou shalt not covet.' I suppose one could covet his neighbor's wife thinking how kind she is and because she bakes great cookies, wishing she were his own. Wouldn't that still be coveting, but for different reasons?
I read the Shepherd of Hermas-- parts of it, haven't finished it it-- when I was young, and in it a man saw a sweet Christian young woman and thought how blessed a man would be to have her as a wife. There could have been some sexual attraction in it. But the 'shepherd' figure in the story rebukes him for his lustful thoughts. After reading that, I began to think about this. If I met a woman I wanted to marry, could I desire to marry her without desiring her to be mine, and was that coveting? Is it possible to marry without lusting since lust is not limited to sex. I believe young people who marry can be pure. As a young man, I had to struggle to avert my gaze. After I met the woman who would be my wife, that seemed like less of a struggle, and I wasn't looking at her and thinking about sex. But I did want her to be my wife, and I tried to go about it in an appropriate way, asking her parents and such, waiting until marriage.
But back to the issue of intention, there are people, young men, at least, who want to keep their minds pure. Some of them may confuse attraction for actual sin or lust. At least the 'adultery in his heart' verse is written about a man who does so intentionally looking with lust, not someone who happens to see a woman he finds attractive. It may be freeing to some men to realize the difference.