One way of demonstrating enthusiastic consent is by participating enthusiastically.
Define "enthusiastic" in a court of law.
Leads right back to the problem of my last paragraph.
Bauglir: I'm arguing from analogy with requiring consent for every act. If not having enthusiastic consent for sex makes it rape, then doesn't not having enthusiastic consent for fondling make it sexual assault?
But let's say you only need it for sex - so women enthusiastically has sex with man once, then later that night, unenthusiastically. Is he a rapist? Also, there's the old example of the married couple where she is willing to have sex with her horny husband to oblige him even though she's not in the mood. Does the fact that she's doing him a favor or just being nice to him, but just kind of laying there, make him a rapist?
Enthusiastic consent also leaves out one fairly commonplace dynamic between men and women - the man wants it more than the woman and has to "seduce" her. Neither would say it was rape. The woman finds it extremely pleasurable after things get going. But at first, he had to overcome her unwillingness to get started. I'm not talking about during sex, which would make it rape (and I'm sure many rapists tell themselves that's exactly what happened) but kissing, feeling up, etc. Hell, it can just as easily be the other way around - he doesn't feel like doing anything and grunts and turns away from her until she starts stroking his junk. Well, those were clear signs he didn't want it, and touching someone's genitals who didn't want it is sexual assault, right? But once her hand is there suddenly he's in a different mood.
And does the enthusiastic consent have to be for the new body part that's being brought in the mix? So they're both topless and making out but he hasn't gone below her waist yet, then he starts taking off her panties. She's not really ready for that but she keeps on doing everything she was doing; they're still kissing and groping and all. Did he have consent to take off her panties? What about if she pushes his hand away from some body part while giving a seductive smile? What is he supposed to make of that?