John had just finished his junior year in college. He had studied philosophy, which raised profound questions about the nature of right and wrong. There was utilitarianism, the idea of striving for the greatest good for the greatest number. He had just finished a course in evolutionary psychology, with its analysis of amoral natural selection as the force behind some of our thoughts and feelings. What mattered most was leaving descendants. Morality and cooperation had their place, but deep down people like all other organisms were selfish -- it wasn't something to be ashamed of.

It was all fascinating. If he took his liberal education seriously, the point was not just to stuff your head full of knowledge. If what you learned mattered, you should be open to living your life differently. He was now trying to do that -- to question old assumptions, to do what was important and avoid what wasn't.

Hiking made him feel good, especially in beautiful countryside like this. It was also good exercise, and combining two things was a good way to maximize utility. It was May, and the semester was over. He walked quickly down the forest trail. It was fairly level here, though he'd been up and down a few hills already. The descent from the last one had been quite steep. Now the conifers were thinning and he saw a meadow ahead -- filled with wildflowers. Definitely a little utility bump from that.

He was in Virginia on a seldom-used and obscure trail and he looked forward to passing the day alone, without running into other hikers. He had decided that the utility for him in avoiding others outweighed the utility from the more spectacular scenery that drew more hikers. The problem was that when he met someone, there were choices to make. Social choices. He could totally ignore them, or make brief eye contact, or nod his head, or mumble,"Hi". He would never stop and try to make conversation, but sometimes others did. But if they stopped to talk, it was an awkward social situation.

With the meadow on his right and scrub forest on his left, he noticed the double blaze that signaled something unusual about the trail ahead. He paused, and as he did, he heard sounds coming from his left. Another hiker. Rats! He then saw that the trail turned sharply to the left, which explained the double blaze.

It was a woman who came into view. Above well-worn hiking books were gray socks, and then a pair of smooth, lovely legs, leading up to blue shorts. Above the shorts was a yellow T-shirt. On her back was a full frame pack. She had reddish-blond hair cut short, blue eyes and quite an attractive face. Quite a pretty girl. She looked to be roughly his age, face glowing softly with health and vitality.

"Hi," she said as she came up to him, slowing her pace. "Didn't think I'd see anybody else out here today."

A conversationalist. Ugh! "Right, me neither," he said, and walked past her. Negative utility. But...

But then he stopped. This was just the sort of girl he was trying to meet. There was a large utility cost to making conversation, to reaching out, but the expected gain from finding a girlfriend was high -- should be high enough to justify the short-term cost of awkwardness.

"Wait," he said.

The girl stopped and turned. She was really quite pretty. Petite -- maybe 5'2" to his 6'1".

He had always just assumed he wanted a girlfriend. But did he? What did utility say? What did evo psych say? "I would like to have sex with you." Hmmm. He realized that was an unusual thing to say. He had always been a bit awkward socially, but he shouldn't be bound by social conventions.

"Right," she said, shaking her head. "I would not like to have sex with you," and she turned to walk away.

He followed her. Someone had told him that the way to really connect with people was to be himself, to say what was on his mind. "I would find sex very pleasurable," he said. "You would too, I believe. It is a natural human instinct. We both would have pleasure. A win-win situation."

"Bye," she said, walking a little faster.

He matched her pace and raised it a bit. Selfishness. Sometimes selfishness was good. He put a hand on her pack, and she slowed.

"Let me go!" she said with some heat.

"I don't want to let you go. I want to have sex with you. I realize you are reluctant. But I figure we could talk this out. Think about the cost-benefit analysis."

"I'll scream," she said.

"There's no one else for miles around," he said.

"I passed someone a mile or so back," she said, meeting his gaze and then looking away.

"I don't believe you," he said. "It's very low probability that you're telling the truth about that. I'm trying to be rational about this. Explain why you don't want to have sex. What is your cost-benefit analysis? Do you not find sex enjoyable?"

She sighed. "I do under the right circumstances, with the right man at the right time. You are not the right man and this is not the right time."

"Evolutionary psychology can explain our different perspectives," he said. "As a female human, you would invest far more in an offspring than I would. My only obligatory investment is a few minutes of copulation and a small quantity of semen released into your vagina. If a pregnancy does result, my net fitness would be enormously increased."

"Yes, and since this is the situation for male humans, many of them want to mate with me. I as a female have choice. Typically I would choose a male and would allow him exclusive sexual access in return for his agreement to provide resources for our children."

John smiled. "You know this stuff!"

"Or I might find an especially good-looking man who I judge to have high-quality genes. The best is to have both combined in one man. But second best is a male who believes he has exclusive sexual access to me as a starting point. But then I find a father of higher genetic quality and mate with him secretly. My genes are mixed with better ones to increase the success of my offspring for a generation or two, while the other man helps raise them."

"And do you judge me not to be of high genetic quality?"

She met his gaze for an instant and looked away. "I am not in a stable relationship with a man who would help me raise children. It is to my strong advantage to delay sex until I am in such a relationship. But actually this is all irrelevant. I am not fertile."

"How do you know?"

She shifted her weight from one foot to the other. "I'm on the pill."

"You may well be lying. It is worth my while to try to impregnate you even if the chances of success are low, because of the huge potential payoff."

"This is all irrelevant in the modern era. I would surely have an abortion if you were to rape me and I were to get pregnant."

"Once again, there is some chance that you would not elect to have an abortion."

"Have no you decency?" she cried. "No sense of right and wrong? The golden rule?"

He liked it better when she talked about utility. "I am trying to ignore such sentimental considerations. Right and wrong have no objective basis. Social rules are worth obeying within a small community where your relatives for instance might punish me. But we are anonymous strangers."

"Listen," she said. "You have laid out evolutionary reasons why you are constructed to have certain preferences. But we are rational humans. We can set those aside. Why should you be a slave to your inclinations? Your genes may have built you to want to leave offspring, but you don't have to accept that."

"We could set them aside. But in the absence of overriding considerations, I have chosen to align myself with my evolutionary make-up."

"I haven't. I use my thoughts to override my instincts and do what I think is important. To do what is moral."

"But you yourself were suggesting that the reason you do not want sex is because of adverse consequences to your fitness."

"Yes!"

"But you as a rational person know that you will not suffer the consequence of an unwanted pregnancy. So why not transcend your own evolutionarily specified tendencies?"

She looked at him and sighed, and started to walk away. He grabbed her pack once more. She pulled away hard, but he kept his hold.

She looked at him a moment. "So, are you going to rape me?"

He thought. "Yes, if you aren't willing, that is what I'm going to do."

"Well, then let's get this over with," she said, shrugging her pack to the ground beside the trail.

John smiled and let his pack slide to the ground, but as he did, the woman sprinted away down the trail the way she had come.

John gave chase. She was fast! But he was faster, and his longer stride gave him more choice in his footing over the roots and rocks on the trail. Before she had gone a hundred yards, he grabbed her around the middle and they tumbled to the ground together.

"Oh, shit," she murmured between panted breaths.

"That wasn't nice," he said as they lay panting, her face down in the dirt, him face down on top of her. "I am stronger and faster than you. You should realize you will pay a penalty for trying to resist me. Let me see..." He found her arm and put his hands on it the way you hold a baseball bat. He then twisted one in one direction, the other in the other -- what he had been raised to call an Indian sunburn.

"Ow," she said softly.

"Do you agree not to try to run away again or resist me?"

She hesitated. He twisted his hands again, harder.

"Yes! I agree."

He smiled, and as he lay on her, he slid a hand up between her legs to her crotch.

"Hey!" she said.

He was momentarily embarrassed and removed his hand, but summoned logic. "Well, we were talking about sex. Surely I'm going to invade your personal space."

He slid his hand up between her thighs again. His cock was hardening in his shorts. He could do her like this, face down on the trail. It would be sufficient for his attempt at impregnation. But he also wanted to enjoy the experience. That was part of his expected utility too. Two benefits to a single activity. The meadow was nicer. "Let's go back to your pack."

She got up, giving him a dirty look, and headed back, retracing the route of the chase. "I think we should talk about this more," she said over her shoulder. "Certainly you can see that I evaluated this as being so strongly against my interest that I was willing to abandon my valuable camping equipment and make a low-probability escape attempt."

"Yes, I can see that," he said. "But the thing is, I'm thinking of maximizing utility."

"Doesn't the knowledge that this will have a huge negative impact on my utility weigh in your own calculations?"

"A little, but not much. When it comes right down to it, I'm maximizing my own utility, and willing to do so at the expense of yours. It's the rational thing to do."

"Before you were arguing that it would increase my utility."

"True, but that was an attempt to get you to agree. Your cooperation would make this a higher-probability venture, so your agreement would help my utility whether my arguments were valid or not."

"Won't it be unpleasant if I'm struggling and crying and screaming?"

He smiled.

"Oh, no ... You're not one of those guys who would find that, um, increases your utility?"

"No," he said. "But as I showed you back there, I am willing to hurt you if you don't do what I want. So if you don't think you can actually dissuade me from ejaculating in your vagina..." He felt a strong pulse of blood as he said that, " ... it's in your interest to be cooperative. I imagine struggling and crying is inherently unpleasant, and if I punish you for them it is even more so."

She bit her lip. "What if I've got HIV?"

"That's very low probability, and besides, female-to-male transmission is exceedingly rare in western populations."

"And what if you have HIV?" she said. "No, don't tell me ... it's your utility you're interested in here, not mine. Do you have HIV?"

"No," he said, then added, "though I suppose it would be in my interest to say I didn't even if I did, in order to minimize the chances of your struggling more."

She looked at him, tears welling up in her eyes.

He felt a brief pang of compassion, but quashed it. His utility was what counted.

"Want to have lunch first?" she said. "I've got a couple roast beef sandwiches. You could have one."

It did sound good, but...

"Or both," she said, and he thought she suppressed a smile.

Yes, she would gladly give both of her roast beef sandwiches to avoid getting raped -- that is, this sex against her will.

"No, the chances of someone coming along are small, but they aren't zero. I think we need to get on with this."

"Even if I'm not struggling, you know this is rape, right?"

"Yes, I know that," he said, looking around. "Over there," he said, pointing to a level patch of grass ten feet off the trail.

"So close to the trail?" she said. "What if someone comes along ... Oh dear, here I am thinking about embarrassment when I should want to maximize the chances of detection."

"Good point," he said. Since his interests were the opposite of hers in this case, he said, "Let's go over that rise ... bring your pack ... and mine too."