Could you explain briefly how reason tells us that humans have a soul? And do other higher animals, such as dolphins and elephants also have souls? Or is it unique to humans?
Here's a brief summary of Aristotle's thoughts on the topic. He was a man of reason, not a man of faith.
His teachings, expressed very shortly, are that chairs and roosters and humans are different things. They are different things because they have different forms. The form of a thing tell us
what it is. Matter alone is just potentiality. Matter compounded with form is what makes
things.
There are non-living things and living things. The soul is the form and the animating principle of a living thing. Living things have powers that non-living things do not possess. The soul is the cause and the source of those powers.
Different living things exist in a nested hierarchy. All living things have the power of growth, nutrition, and reproduction. Animals also have the powers of locomotion and perception. Rational beings also have the powers of the intellect. So yes, dolphins and elephants have souls, but their souls are of a different nature than the souls of man, because humans are rational creatures.
It's worth noting that virtually every metaphysics reasoned out by the various cultures around the world
except materialism comes to the conclusion that there is something like a soul. Materialism is an incoherent anomaly that happens to have a privileged position in our age.
Of course, different schools of thoughts have done a better or worse job of mapping exactly what the soul is and how it works (just like different scientists have done a better or worse job of mapping the physical laws of nature). But the idea that the existence of a soul doesn't originate in Christian scripture or arise as a tenant of faith. It arises when people try to answer the question:
what are we?I remember this discussion from many years ago, but I don't remember your argument. If you made it then - I seem to remember you NOT being a faithless wretch back then.
You must be misremembering, because I've always been pretty faithless. It's a flaw of mine that I'm trying to remedy. It's not easy.
Does everyone who supports this also support financially supporting that child? Health care, education, child care, food, and all those expenses for 18 years.
No definitely not. I don't think it is a good thing to build the state infrastructure required to provide that to the orphan children, and there would be something unjust in the state taking it from others by force in order to give it to the orphans. I think that approach you advocate for will give us very bad results.
One could have legitimate opposed slavery while at the same time opposing "forty acres and a mule". Slavery was an abomination. Abortion is an abomination. They are both deeply offensive to the dignity of man and, like slavery, abortion must be seen clearly by society as soon as possible. We are murdering children by the millions. It is evil and it is destroying us.
The question of how we care for those who are unloved is a provincial question. Children are owed the love and care of their parents. When the parents fail to fulfill their responsibilities to their children, it is a tragedy. We can be good people who desire to fix that evil without concluding that we need to build a massive state to do so.
There are no bright distinguishing lines between a fetus and a baby.
Then again there are no bright distinguishing lines between a human and a non-human.
Abortion is a form of murder perhaps.
But so is killing pigs & cows.
Between the death of a fetus and the death of a cow, I don't know which is the most tragic or the worst crime.
And yet I'm not a vegetarian, far from it. If I was ever to be judged for my crimes, I think my non-vegetarianism would condemn me to hell, far more than my support for abortion rights for women.
This is the confusion that materialism leads to. If things don't have form -- if things
aren't things -- then of course morality has no firm basis to be built upon, and you cannot think clearly about anything. We get what we have today: people blindly pawing at the moral truth, built on intuitions, popular belief, and small direct insight, without any structural guidance, resulting in a combination of complete impotency to see the truth in some respects, while zealously exaggerating the truth in other respects.
If we can't distinguish between a fly and a human, or between a human and a tree, then we are far, far away from being able to talk about rights and morality in any intelligent way.
And that's what we're seeing today. Many people, in a misguided desire to bring the clarity of science to all disciplines of knowledge, have instead begun limiting knowledge to only those places that science can illuminate, leaving the rest of the giant library of potential human knowledge dark. The old systems of thought provide less reassurance (in a way) than science, but greater illumination.
I consider myself pro-choice , meaning we are responsible and accountable for our choices even those overly influenced by our hormones.
The Pro Choice movement tends to define THE choice as being after sex (assuming the majority of unwanted pregnancies' occur after consensual sex) That's a problem. Abortion ought not be relied on as a birth control choice.
If the Pro-Life movement chooses to force individuals who may not hold the same values, to save the lives of the unborn they must also provide the means to give that child the best chances in the "pursuit of happiness". The GOP is generally regarded as the pro-life party, yet at the same time works against any social safety net... is a problem.
The right wants a social safety net, and they often provide one. They do not want an over-reaching state, which they believe causes many more problems than it solves. You can care about your neighbors without being a statist who imagines every physical need people might have can be attended to by a bureaucracy, monopolized violence, and taxes. That's a really absurd assertion.
The extremes not only don't want abortion, they want to limit access to contraception as well. The furthest extremes even say that masturbation is wrong.
Yes. Freedom and self-expression are not the only virtues. Chastity and temperance are also virtues. When, as a society, we encourage wild disorder of the sexual appetite, we create massive problems in our society and our culture. Problems we are all seeing today. Our society is diseased. One of the root causes of that disease is the sexual revolution. Contraception as at the forefront of that. When you're treating a disease, it is usually wise to focus on the root cause, not on the various symptoms that arise as a result. When someone has a heart disease, you treat the heart.
It is not good that people have started treating sex primarily as a tool of self-gratification and entertainment. Sex is properly ordered towards procreation and the strengthening of a marriage. Strong married couples are the foundation of society.
They are the primary social safety net that people like me believe in. They can do the things that you wrongly imagine the state can accomplish. Children deserve their parents, not a bureaucrat. When we tear down all of the boundaries around sex, we tear down marriage and tear down the most important unit of society: the family. In doing so, we all suffer.
So yes, I definitely oppose contraception. And if you're asking my advice, yes, avoid masturbation too. Get married, attend to your relationship like a careful gardener, sleep with your wife regularly, love her with all of your heart, make lots of beautiful children, and be happy.
I cant speak to Joshua's motives, I'm speaking generically about the vast swath of "pro-life" people. That society's responsibility to "protect the child" somehow ends with delivery.
This isn't even close to true. The pro-life movement also opposes murder of a person after they are born. People shouldn't be murdered. It's pretty fundamental.
If you want to talk about to what degree a society should build governmental structures to assist those in need, we can have that conversation. It's a provincial question where I imagine you and I will share some common ground (and may even share some criticisms of the republican-right). But you don't get to import it into the conversation about murder.
It's like saying "Oh right, you oppose the murder of the homeless, so why don't you take them into your house and clothe and feed them? Hypocrite!" It's absurd.
Fenring is quite right though, the argument is really fundamentally about personhood and the right to life. One view is shrouded in superstition and mysticism about the "soul", the other is based on consistent scientific analysis that recognizes brain death, which when there is no brain is a, well, no-brainer.
Philosophy isn't "superstition" or "mysticism". It is reason.
Materialism is incoherent. It doesn't work. I understand the allure of reducing everything to a scientific inquiry, but it collapses. You see it right here in this thread. Science is a great but limited tool. There are things that we can know -- actually know, not just imagine or believe via superstition -- using tools other than science. When we refuse to use those tools, we neuter our minds and we do harm to ourselves and others.
Is the uniqueness of the DNA really what's important here?
I won't speak for msquared, but for my part: no. What is important is that the unborn child is an independent person. The fact that he hasn't yet developed a particular physical feature that people have -- like a brain or nervous system or eyes -- does not change what he
is. He
is a person. That is his nature. It is the same fundamental nature as me or you. Just like you and I should not be murdered (even if we happened to go blind or brain-dead) neither should the unborn child.
Further problems arise because about 3/4 of the fertilized eggs do not attach to the womb and are spontaneously aborted.
Are they human lives? Shouldn't we be trying to stop that horrible slaughter, too? 
Yes they are human lives. It is a sad thing when a human life is lost through the natural processes of the body, but it's not akin to abortion. It's like saying 'well my uncle died of old age yesterday, so if you oppose murder, shouldn't you also oppose death-from-aging!?' It's a silly statement.
Biology is messy. There are few bright lines between states: human and non-human, alive and dead, male and female, person and non-person. Creating such a bright line is more imposing your own prejudices than making anything clear.
I promise, things are more clear once you can actually distinguish between things and have some sort of sensible metaphysics. Materialism is a cloud of hazy confusion. Come stand over here for a while and at some point you'll find yourself looking around saying "oh, well, that made everything a lot more clear. Why did I resist using all of the knowledge available for so long?"
A fertilized human egg is not a human being. It has the potential to become one, IF it is captured in a womb and IF it comes to full term and nothing major goes wrong. Until then, it is only developing. Giving it more status than that is not scientific.
"Person status" is not a scientific term. Science has
no idea and
no capacity to talk about persons or morality. These are metaphysical concepts. Science is a subset of human knowledge and it is blind to metaphysics. It is only concerned with the material world. Of course giving any person anywhere a metaphysical "status" is not scientific. That's the whole point. Science isn't the only crucible of truth. It's really cool, but ultimately really limited. There are other disciplines of knowledge that are essential. If you close your eyes to them, you can't know anything about morality in any systemic or coherent way, and that's a really important thing to have.
The fact that we get into these detailed and somewhat silly arguments about genetics demonstrates that you can apply a complex concept like "personhood" to the development stages of a person. 
The fact that people argue about things doesn't demonstrate anything but that people argue. The truth is the truth. People have always had trouble seeing it. If you were sitting in the back of a bar-room in 1800 as some abolitionists and slavers debated the merits and evils of slavery, you might similarly say "The fact that we can get into these detailed and somewhat silly arguments about 'species' demonstrates that ..." and you might think it's a clever or insightful statement, but you'd just be wrong. Black people are humans just like me and you, contrary to whatever some dumb things people said about sub-species (often in the name of science) 200 years ago. Similarly, an unborn child is a person, just like me and you, despite the fact that people are making arguments otherwise.