Chapter Eight: Fantasy vs. Lust
Thinking About Sex
God established marriage, therefore he wants people to get married. God created us male and female and told us to fill the Earth, which means he wants us to have sex. God also gave us brains, so he wants us to think. And since our brains don't have an off-switch other than sleep, our minds have to think about something while we're having sex. There are 3 possibilities for sexual thoughts:
Lust means you're thinking about a real-life desire to have sex with someone or something other than your spouse, and the Bible says clearly and repeatedly that this form of thinking about sex is sinful.
However, it's also possible to think about having sex with your spouse, or a potential spouse if you're single, and that is not lust, because even though it's a real-life desire, the object of your desire is an acceptable person. In the case of a sexual desire for a potential spouse, it's not lust as long as your real desire is based on getting married before fulfilling that desire.
That's a kind of legalistic explanation. The simple explanation is that thinking about sex is a normal, healthy, non-sinful part of marriage and of looking for a husband or wife. When looking for a spouse, sexual compatibility should not be the only consideration, but unless you're being subjected to an arranged marriage, it should be one part of the equation.
So, a real-life desire for acceptable sex is not lust. It's just part of normal married life, or before marriage as part of what motivates us in seeking a spouse. You see a good looking guy, you find out he's single, you pursue him or hope he pursues you, and you think about what it might be like to have sex with him. That's not lust, that's fantasizing to evaluate possibilities and consider if he might or might not be compatible enough to marry.
You can read more about compatibility issues in the Before Marriage chapter.
And that brings us to the third way to think about sex: fantasy.