On this issue I'm not a propertarian.  I simply view it as a right to life argument and that all killing is wrong, and that's usually where I end.  However, I recently got into a debate with a pro-choice propertarian over the issue of abortion.  It was civil, although fierce, but I came to a new property rights pro-life view.

First, we must define a few terms and throw out some arguments that have no basis or simply make no sense.

What is life?  This should be a fairly obvious answer:  any organic organism which is not dead (a definition can be found here or here).  However, there is obviously something that separates us from plants and that is sentience, awareness, or conciousness.  This is what makes life all worthwhile and what makes it so scary to lose.  Now, animals are also sentient, but our amount of awareness is much greater, which is what separates us from them.  But why am I talking about this?  Because there are a few arguments that can be dispelled by this definition on both sides, mainly, "when does life begin?"

Many Christian pro-lifers want to assert that life begins at conception because that's when a soul enters the body.  This, however, is for me an inadequate argument as there is no scientific or conclusive proof, only the dualist argument, that there even is a soul.  And even if there is, there is no way to prove when it "enters" the body, if it "enters" at all.

As for pro-choicers, they want to say that life begins once the baby is born.  I also don't find this argument compelling.  What is the significance of this event (of course it's significant, but how does this make you "alive"?)  Is it that first breath?  Many babies don't breathe the second they're born, does that mean they could still be aborted if they don't breathe right away?  Does my brain, and my heart, and my other organs encased in my own body not make me alive?  Maybe not, but my first breath certainly doesn't.

Instead, we should look to the characteristic of our being that makes us fully human.  Now where this begins is not settled.  Some people believe it's once a fetus can have dreams; others believe that a very young fetus can feel what's going on inside the womb and react to that; while others believe it isn't until 2 or 3 years old, when the child becomes self-aware.  Since we don't really know at this point in time, I suggest that we concede that all stages of life are sentient for the sake of cooperation.  I myself would have a hard time arguing for the allowance of anything that could possibly become sentient to be killed, but that's just me.

The fetus is the woman's property.  This argument is especially dangerous, even if you think that life begins at birth as it potentially allows for approval of slavery.  If the fetus is property, then once it is born it is also property, which means that a baby can be legally sold as it has no rights whatsoever.  Instead, we will say that the fetus (a separate entity or life) is occupying your body (your property), and that's where we will being with the argument:

Argument #1.  The fetus has no choice in being there.  It is forced to be there and has no way to leave until birth.  If it has another option, I'm sure it would choose to leave a mother that did not want it, but it can't.  You always have the right to remove anyone from your property, but you don't have the right to kill them.  This applies directly to the fetus as there is but two choices, birth (or removal once viability has been reached) or death.

Argument #2.  Some people assert that the fetus is "invited."  This view is absurd, as a person who is invited onto another's property has the choice of whether or not to accept the invitation.  Although, some people will continue and say that the fetus "accepted" the invitation by being conceived and coming into existence.  This, however, still does not work as a guest always has the ability to leave whenever they so choose as a fetus does not.  It also assigns a confusing amount of agency to a fetus which is not granted full human rights.

Argument #3.  The fetus and the mother are engaged in a legal contract.  As a fetus cannot write or speak (written or oral contracts), it must be an implied contract.  An implied contract is one in which the actions of the two-parties involved suggest that they understand the terms of the contract and are willing to accept them.  There are many implied contracts that we engage in every day.  When we watch someone's property for them, it is implied that we won't take, damage, or misuse that property.  When we go to the grocery store, it is implied that we will select what we want without damaging other goods and then pay the bill.

The same goes for sex.  When we engage in consensual sexual activity, we know that the result could be pregnancy.  We understand the risk and therefore have entered into the implied contract.  Intent does not matter, as we also know that contraceptives are not 100% effective and pregnancy could still result.  Similarly, when you go skydiving the intent isn't to die, but it certainly is an understood possiblity.  For most people, the intent of recreational sex is not to get pregnant, but the possibility is understood and therefore you have engaged in the implied contract with the future fetus.

Now the contract on the end of the fetus is very simple.  By being conceived it obviously wants to be born.  The only thing it must do is continue to grow and have a successful birth without harming the mother or putting her life in danger as she still has the right to life.

The contract for the mother is a little bit more complex.  The mother cannot harm the fetus as all people want to be born healthy and without mutations or defects.  The fetus owns its own body and has the right to life, just like all people.  The mother is also the one who gets to decide to abort the fetus but only if the fetus has broken the contract by harming the mother or putting her life in danger.  This is an exceptional responsibility as the fetus has no way to end the contract if the mother breaks it by harming it, and ending the contract always results in death for the fetus.

Now, by no means do I suggest making abortion illegal at this time.  Because of the nature of laws and what constitutes a just law, this would not be just.  Only once the people find abortion to be absolutely immoral, then and only then can we make abortion illegal; otherwise women will simply be having dangerous abortions in back alleys.  We also need to have better foster care, adoption, and parental help programs (privately run of course) set aside to help those who need it.