I am actually not entirely against a system where people are qualified as capable of consenting. It is possible to qualify a person for a drivers license on an individual basis, I don't see why it is not possible to qualify people for ability to consent on an individual basis. It wouldn't make much sense to say that everybody of a certain age can drive, would it? The only reason I am against such a system is that it seems to involve a centralized authority, and I am against the idea of giving some arbitrary bureaucratic agency the ability to determine who is capable of engaging in sex, just as I am against the idea that the government decides who is capable of driving on roads (rather it should be decided by private road owners). On the other hand, it isn't as if we do not already have a centralized authority determining the age at which a person is capable of consent, it seems better if they decide these things based upon individual evidence of competency rather than arbitrarily. I never said that the morality that some sort of qualifier is required to engage in sexual activity is arbitrary, rather your specific qualifier is arbitrary, it is artificial and it is a recent social construct as well. Do you pull these ages out of your ass as well? You answered the question "why 18 instead of 17" with the claim that a line needs to be drawn somewhere, without further clarification this is apparently synonymous with saying "because there must be some age, and the age is 18, the age ought to 18". This seems to be arbitrary as well. What is so special about 20 year olds that makes it so that they can have consensual sex with a 15 year old, but a 21 year old cannot? And what is so special about an 18 year old, that they can have sex with a 13 year old but a 19 year old cannot? Do you think that a 13 year old is capable of consenting to sex with an 18 year old, but on the day the 18 year old turns 19 they suddenly possess some exploitative power over the 13 year old? Or that the day a 12 year old turns 13 they suddenly gain some wisdom allowing them to engage in sexual activity with an 18 year old without it being exploitative? Your logic is apparently arbitrary, or you believe in some magical process that takes place on certain birthdays (am I the only one who notices a pattern of people associating magic to sexual things involving those under the age of 18?), or perhaps you do not take issue with consent at all but rather have some other driving motivation to prohibit certain people from engaging in sexual activity with certain others. You say a lot of things without qualifying them. What is unhealthy about a 14 year old sleeping with a 20 year old that becomes healthy if the 14 year old becomes 15 before they 20 year old becomes 21? Does a 20 year old not have the same power of suggestion over a 15 year old as a 21 year old does? I actually quite explicitly stated that the sexual desires of most men are not moral justifications, when I pointed out that most men are evolutionarily programmed to rape but that rape is immoral. The core of my argument is that people who can consent to have sex with each other should be allowed do engage in sexual relationships with each other. I suppose that we must then define what consent is. Consent is not just the ability to agree to do something - a five year old can be asked to engage in sexual activity and proceed to do so, however it is apparent that they do not have the ability to consent. The reason we would say that the five year old cannot consent is due to the fact that they do not comprehend the implications of what they are being asked to do. A bomb could be placed in a box with a button on it, configured such that if the button is pressed the bomb explodes. If I hand a person this box and ask them to press the button, it does not mean that they consent to be killed if they press the button. Consent requires a well rounded understanding of the potential consequences of a taken action. Consent is not just the taking of an action while understanding the potential consequences of the action. If I place a bomb in a box as before, although this time I explain the details of the scenario to the person whom I ask to press the button, they have not consented to press the button if they only do so because I am holding a gun to the head of one of their loved ones. Consent requires a true desire to take an action, independently of external coercion. This is not to say that a person cannot take actions they regret having to take to reach a certain goal. For example, a person who has a desperately impoverished family but who also has a life insurance policy, may have a true desire to commit suicide in order to provide for their family. They can consent to be shot even though they would prefer not to be, because their desire to provide for their family outweighs their desire to live. The difference is that, in the case of the intentional suicide, the person took action based on their own cognition (ie: the idea to commit suicide to save their family arose from their own mind, and was not forced upon them by the malicious actions of another). Admittedly the distinction is hard to qualify, however I believe that we can agree that consent requires a true desire to take an action and that the desire can not have been brought to be by the rights violating activity of another person. I believe that this enough to define consent. Consent is the taking of an action, while having a reasonable understanding of the potential consequences of the action, while having a true desire to take the action, without the desire stemming from the malicious rights violation of another party. Thus we can conclude that a person is capable of consenting to sex if they have a reasonable understanding of the potential consequences of engaging in sex and they still desire to engage in sex of their own free will. The reason rape is immoral is because inherently somebody who is raped does not desire to be raped of their own free will. Even if men are biologically programmed to desire rape, it is immoral to rape for the previously stated reason. A five year old is incapable of consenting to sex because they are incapable of having a reasonable understanding of (and appreciation for) the consequences of engaging in sexual activities. Your five year age gap clearly shows that consent is not the issue you have with underage sex. If a 14 year old is capable of understanding and appreciating the potential consequences of sex, and they still decide to engage in sexual activity of their own free will, then they are capable of consenting to sexual interaction with a 30 year old just as well as they are capable of consenting to engage in sexual activity with a 19 year old. My argument is that a 14 year old is capable of knowing and appreciating the potential consequences of sexual activity as well as naturally biologically programmed to desire to engage in sexual activity of their own free will. A five year old is not biologically programmed to desire to engage in sexual activity, any desire a five year old has to engage in sexual activity is going to be a desire that comes from coercion (and additionally a 5 year old is not capable of understanding and appreciating the potential consequences of engaging in sexual activity). In addition to a 14 year old being able to understand and appreciate the potential consequences of engaging in sexual activity, and being biologically programmed to desire to engage in sexual activity, males are biologically programmed to desire to engage in sexual activity with 14 year olds (as per my previous logical analysis of males desire for youth and fertility), and therefor it is not immoral for adult males to engage in sexual activity with 14 year olds. And again you like to use words without defining them. What is virtue? What makes a person virtuous. What is the property of being virtuous? Something that tends towards 'the good'? What is the Good then? I assume the Good is the expression of virtue, since that would complete your circular logic. I also don't see anything immoral about the finite (whatever the hell you mean by that, I suppose), and I definitely don't see anything immoral with materialism. Also, 14 year olds also have sexual desires, as they are biologically programmed to.