Tag Archives: Atheism

William Lane Craig debates Austin Dacey: Does God Exist?

Here is the video and summary of a debate between Christian theist William Lane Craig and Austin Dacey at Purdue University in 2004 about the existence of God.

The debaters:

The video: (2 hours)

The video shows the speakers and powerpoint slides of their arguments. Austin Dacey is one of the top atheist debaters, and I would put him second to Peter Millican alone, with Walter Sinnott-Armstrong in third place. This is the debate to show people who are new to apologetics. The debate with Peter Millican is better for advanced students, and that’s no surprise since he teaches at Oxford University and is familiar with all of Dr. Craig’s work. The Craig-Dacey debate is the one that I give to my co-workers.

By the way, you can get the DVDs and CDs for the first Craig-Dacey debate and the second Craig-Dacey debate and the second Craig-Sinnott-Armstrong debate. The Peter Millican debate is not available on DVD, but the link above (Peter Millican) has the video and my summary.

Dr. Dacey’s 5 arguments below are all good arguments that you find in the academic literature. He is also an effective and engaging speaker, This is a great debate to watch!

SUMMARY of the opening speeches:

Dr. Craig’s opening statement:

Dr. Craig will present six reasons why God exists:

  1. (Contingency argument) God is the best explanation of why something exists rather than nothing
  2. (Cosmological argument)  God’s existence is implied by the origin of the universe
  3. (Fine-tuning argument) The fine-tuning of the universe for intelligent life points to a designer of the cosmos
  4. (Moral argument) God is the best explanation for the existence of objective moral values and objective moral duties
  5. (Miracles argument) The historical facts surrounding the life, death and resurrection of Jesus
  6. (Religious experience) God’s existence is directly knowable even apart from arguments

Dr. Dacey’s opening argument:

There are two ways to disprove God’s existence, by showing that the concept of God is self-contradictory, or by showing that certain facts about ourselves and the world are incompatible with what we would expect to be true if God did exist. Dr. Dacey will focus on the second kind of argument.

  1. The hiddenness of God
  2. The success of science in explaining nature without needing a supernatural agency
  3. The dependence of mind on physical processes in the brain
  4. Naturalistic evolution
  5. The existence of gratuitous / pointless evil and suffering

One final point:

One thing that I have to point out is that Dr. Dacey quotes Brian Greene during the debate to counter Dr. Craig’s cosmological argument. Dr. Craig could not respond because he can’t see the context of the quote. However, Dr. Craig had a rematch with Dr. Dacey where was able to read the context of the quote and defuse Dr. Dacey’s objection. This is what he wrote in his August 2005 newsletter after the re-match:

The following week, I was off an another three-day trip, this time to California State University at Fresno. As part of a week of campus outreach the Veritas Forum scheduled a debate on the existence of God between me and Austin Dacey, whom I had debated last spring at Purdue University. In preparation for the rematch I adopted two strategies: (1) Since Dacey had come to the Purdue debate with prepared speeches, I decided to throw him for a loop by offering a different set of arguments for God, so that his canned objections wouldn’t apply. I chose to focus on the cosmological argument, giving four separate arguments for the beginning of the universe, and on the evidence for Jesus’ resurrection. (2) I reviewed our previous debate carefully, preparing critiques of his five atheistic arguments. In the process I found that he had seriously misunderstood or misrepresented a statement by a scientist on the Big Bang; so I brought along the book itself in case Dacey quoted this source again. I figured he might change his arguments just as I was doing; but I wanted to be ready in case he used his old arguments again.

[…]The auditorium was packed that night for the debate, and I later learned that there were overflow rooms, too. To my surprise Dr. Dacey gave the very same case he had presented at Purdue; so he really got clobbered on those arguments. Because he wasn’t prepared for my new arguments, he didn’t even respond to two of my arguments for the beginning of the universe, though he did a credible job responding to the others. I was pleased when he attacked the Big Bang by quoting the same scientist as before, because I then held up the book, specified the page number, and proceeded to quote the context to show what the scientist really meant.

Dr. Craig is always prepared!

William Lane Craig lectures on naturalism at the University of St. Andrews

Lets take a closer look at a puzzle
Lets take a closer look at a puzzle

Note: even if you have heard Dr. Craig’s arguments before, I recommend jumping to the 48 minutes of Q&A time, which starts 72 minutes in.

About Dr. William Lane Craig:

William Lane Craig (born August 23, 1949) is an American analytic philosopher, philosophical theologian, and Christian apologist. He is known for his work on the philosophy of time and the philosophy of religion, specifically the existence of God and the defense of Christian theism. He has authored or edited over 30 books including The Kalam Cosmological Argument (1979), Theism, Atheism and Big Bang Cosmology(co-authored with Quentin Smith, 1993), Time and Eternity: Exploring God’s Relationship to Time (2001), and Einstein, Relativity and Absolute Simultaneity (co-edited with Quentin Smith, 2007).

Craig received a Bachelor of Arts degree in communications from Wheaton College, Illinois, in 1971 and two summa cum laudemaster’s degrees from Trinity Evangelical Divinity School in Deerfield, Illinois, in 1975, in philosophy of religion and ecclesiastical history. He earned a Ph.D. in philosophy under John Hick at the University of Birmingham, England in 1977 and a Th.D. underWolfhart Pannenberg at the University of Munich, Germany in 1984.

Dr. Craig was in Scotland to lecture at a physics conference, but a local church organized this public lecture at the University of St. Andrews.

Here is the full lecture with Q&A: (2 hours)

Summary:

  • Naturalism defined: the physical world (matter, space and time) is all that exists
  • Dr. Craig will present 7 reasons why naturalism is false
  • 1) the contingency argument
  • 2) the kalam cosmological argument
  • 3) the fine-tuning of the universe for intelligent life
  • 4) the moral argument
  • 5) the ontological argument
  • 6) the resurrection of Jesus
  • 7) religious experience

Dr. Craig does mention an 8th argument early in the Q&A – the argument from the non-physicality of mental states (substance dualism), which is an argument that I find convincing, because a materialist conception of mind is not compatible with rationality, consciousness and moral agency.

Questions and Answers

He gets a couple of questions on the moral argument early on – one of them tries to put forward an evolutionary explanation for “moral” behaviors. There’s another question the definition of naturalism. There is a bonehead question about the non-existence of Jesus based on a Youtube movie he saw – which Craig responds to with agnostic historian Bart Ehrman’s book on that topic. There’s a question about God as the ground for morality – does morality come from his will or nature.

Then there is a question about the multiverse, which came up at the physics conference Dr. Craig attended the day before. There is a good question about the Big Bang theory and the initial singularity at time t=0. Another good question about transfinite arithmetic, cardinality and set theory. One questioner asks about the resurrection argument. The questioner asks if we can use the origin of the disciples belief as an argument when other religions have people who are willing to die for their claims. One of the questioners asks about whether the laws of nature break down at 10^-43 after the beginning of the universe. There is a question about the religious experience argument, and Craig has the opportunity to give his testimony.

I thought that the questions from the Scottish students and faculty were a lot more thoughtful and respectful than at American colleges and universities. Highly recommended.

William Lane Craig debates Daniel Came: Does God exist?

Dr. Craig's opening speech summary slide
Dr. Craig’s opening speech summary slide

The video of the debate was posted by ReasonableFaith.org – Dr. Craig’s organization. This debate occurred in March 2017 at the University of Dublin, in Ireland.

The video: (91 minutes)

My non-snarky summary is below.

Dr. Craig’s opening speech

Two claims:

1. There are good reasons to think that theism is true.
2. There are not comparably good reasons to think that atheism is true.

Five reasons for God’s existence:

1. The beginning of the universe
– actual infinite past is mathematically impossible
– BGV theorem: any universe that is on balance expanding in its history (like ours) cannot be past eternal

2. Fine-tuning of cosmic quantities and constants
– slight changes to quantities and constants prevent a universe from supporting complex embodied life
– the multiverse response of atheists conflicts with observations, e.g. the Boltzmann Brains problem

3. Objective moral values
– God’s existence is required to ground objective moral values and duties

4. Minimal facts case for the resurrection of Jesus
– there are good reasons to accept the most widely accepted facts about the historical Jesus (empty tomb, appearances, early widespread belief in the resurrection)
– the best explanation of these minimal facts is that God raised Jesus from the dead

5. Experience God directly
– in the absence of any defeaters to belief in God, a person can experience God directly

Dr. Daniel Came’s opening speech

1. The hiddenness of God
– if God wants a personal relationship with us, and a relationship with God would be the greatest good for us
– God ought to reveal himself to us, but he does not  reveal himself to many people, the “non-resistant non-believers”

2. The inductive problem of evil
– many evil events occur that are pointless – there is no morally sufficient reason why God would allow them to occur
– examples: animal suffering, children born with disease, tsunamis
– the theistic response to this is that humans are not in a position to know whether there are morally sufficient reasons, due to our limitations of knowing the consequences
– but this ripple effect defense has 4 possible outcomes, 3 of which don’t do the job of justifying

Dr. Craig’s first rebuttal

1. The hiddenness of God
– God’s goal is not to make his existence known, but to draw them into a love relationship
– it’s speculative that overt displays of God’s existence would draw people to him in a love relationship, they might resent his bullying
– atheist would have to prove that God could draw more people into a love relationship with him by revealing himself more overtly

2. The inductive problem of evil
– as humans, we are not in a position to know for certain that any apparently pointless evil really is pointless
– William Alston article: 6 limitations of human knowing make it impossible to judge that an evil is actually “pointless”
– Dr. Came says that there are 4 possibilities for the ripple effects, and since 3 are bad, it’s likely that there are not morally sufficient reasons for a apparently pointless evil
– it is logically fallacious to assert probability conclusions without knowing the probabilities of those 4 options
– there is actually an argument from evil: since the problem of evil requires an objective standard of good and evil by which to measure, and God is the only possible ground of objective morality, then pressing the problem of evil actually requires the atheist to assume God, in order to ground this objective moral standard

Dr. Came’s first rebuttal

3. Objective moral values
– there are naturalistic theories of moral realism where objective moral duties and objective moral values exist in a naturalistic universe
– I’m not saying that any of them are correct, but there are many theories about object morality in a naturalistic universe

There are naturalistic theories for all of the 5 arguments that Dr. Craig presented. It is Dr. Craig’s responsibility to present those naturalistic theories and prove that they are not as good as his explanations. I’m not going to defend (or even name!) a single naturalistic theory for any of these 5 arguments by Dr. Craig.

Dr. Craig’s explanations for the 5 evidences he gave can’t be admitted, because we have to know how God did something in naturalistic terms before we can know that God did it supernaturally. Explanations are only valid if they are naturalistic.

1. The beginning of the universe
– naturalism explains how the universe expands after it came into being, so that explains how it came into being
– the God explanation, that God created the universe out of nothing, is not admissible, because it is not naturalistic
– how does God, as an unembodied mind interact with the physical world?
– the only agency that we know about is human agents, and we have bodies, so how could God perform actions without having a body?

The theistic hypothesis does not make any predictions, but naturalism makes lots of testable predictions. God could do anything, so he is not constrained and is therefore untestable. We can’t infer God as an explanation in principle because we can’t predict what is more probable if God exists than if he does not.

2. Fine-tuning of cosmic quantities and constants
– the university was not set up to make embodied intelligence plausible, because the vast majority of the universe is hostile to life
– there are models of the multiverse that escape the Boltzmann Brains problem that Dr. Craig raised

Dr. Craig’s second rebuttal

Some of Dr. Craig’s arguments are deductive (e.g. – the beginning of the universe, objective moral values), so that the conclusion follows from the premises if the premises are true. The resurrection passes the standard tests for historical explanations.

1. The beginning of the universe
– the whole point of the argument is that there is no naturalistic explanation for an ultimate beginning of the universe

2. Fine-tuning of cosmic quantities and constants
– the whole point of the argument is that there is no naturalistic explanation for a design of the universe to support life
– he has to prove that intelligences has to be attached to bodies
– human beings are non-physical minds united to physical bodies
– naturalistic attempts to explain mental operations fail
– the arguments prove that unembodied minds exist
– the vast expanse of the universe is required in order to form the galaxies, stars and heavy elements needed for complex life
– why expect that the entire universe should be small, or that life would be everywhere?
– a non-fine-tuned world is more likely in the multiverse, and in a multiverse, we are more likely to have a Boltzmann brain world than a world with complex, embodied life
– Dr. Came has not advanced any naturalistic explanation for the fine-tuning

3. Objective moral values
– non-theistic ethical theories cannot account for the ontological foundations of objective moral values and duties
– atheistic theories of moral realism simply assume objective moral values out of thin air
– it is especially hard to find any basis for objective moral duties in the absence of God

Dr. Came’s second rebuttal

5. Religious experience
– Dr. Craig should not bring up religious experience in a debate where arguments and evidence are central
– people who have dreams, hallucinations and psychotic delusions could appeal to religious experience
– religious experience is by no means universal, and it is possible to doubt it

3. Objective moral values
– there are lots of atheists who hold to objective moral values
– Dr. Craig has to explain how God grounds objective moral values and duties
– Dr. Craig has to explain why atheist moral realist theories don’t work to ground objective moral values and duties

1. The beginning of the universe
– Dr. Craig claims that something can’t come from nothing, that’s not an argument
– there are numerous models that don’t require an absolute beginning of the universe
– Dr. Craig cites the BGV theorem, but Guth (one of the authors) says that only the inflation has a beginning, not the whole universe

Dr. Craig’s conclusion

1. The beginning of the universe
– on theism, there is an efficient cause, but no material cause, for the origin of the universe
– on atheism, there is neither an efficient cause nor a material cause, for the origin of the universe: that’s worse!
– if he thinks that there are models of the universe that don’t require a beginning, then let him name a viable eternal model of the universe
– he never refuted the mathematical argues against an infinite past

2. Fine-tuning of cosmic quantities and constants
– nothing to refute

3. Objective moral values
– God is a better ground for morality than humans, because he is ultimate, and not contingent and arbitrary
– God is a being who is worthy of worship, and therefore command his creatures with moral duties

4. Minimal facts case for the resurrection of Jesus
– nothing to refute

5. Religious experience
– only justified because there are no defeaters to it

1. The hiddenness of God
– atheist has to show that if God’s existence were more obvious, that it would result in more people being drawn to him

2. The inductive problem of evil
– Dr. Came’s argument was logically fallacious, and makes errors in probability theory

Dr. Came’s conclusion

Sometimes, people can’t prove something, but lack of evidence is a justification for doubting it, e.g. – werewolves.

If none of Craig’s arguments work, then it follows that it is not rational to believe that God exists, and it is rational to believe that God does not exist.

Atheists shouldn’t have a burden of proof for what they know, only theists have a burden of proof for what they know.

My thoughts

One quick point. If life were common everywhere then atheists would infer that God wasn’t involved in it. Period. “Life is everywhere, so it’s common, why do we need a designer?” they’d say. I agree with Dr. Came about denouncing religious experience in a formal debate. I don’t like when Dr. Craig brings this up, but I see why he does it – he’s an evangelist, and that’s a good thing, too. I just worry about how it looks to atheists, although it’s good for sincere seekers. I’m not the one on the stage, though, Dr. Craig is.

I think the point about more overt revealing by God would annoy people and make them turn away. Think of how gay people respond to the suggestion that there is anything wrong with them, with rage, vandalism, threats, coercion, attempts to get you to lose your job and business, and using government as a weapon to fine and imprison you. It’s really obvious to me that more God does not mean more love of God. For those who don’t want God, the hiddenness is respect for their choice to put pleasure above the search for truth. (I mean the gay activists – I have great sympathy for people who struggle with same-sex unwanted attractions because they were impacted by a failed bond with their parent of the same sex as they are).

Whenever I meet people like Dr. Came, I always urge them to keep investigating and pursuing truth, because they will find it if they are sincerely seeking after God. Some atheists do sincerely seek God, but I don’t know any who haven’t found him. I’m not sure if that’s because those atheists who claim to be non-resistant and rational are in fact resistant and non-rational, or what the real reason is. If you believe the Bible, all unbelief is non-rational and resistant (see Romans 1). Regarding the werewolves, we don’t have any good arguments for werewolves, we do have good arguments for God. Dr. Came didn’t refute the arguments that Craig raised, nor did his own arguments for atheism work. And there are many, many more arguments (origin of life, Cambrian explosion, habitability-discoverability, molecular machines) that Craig did not raise, too.

Is the definition of atheism “a lack of belief in God”?

I have a key that will unlock a puzzling mystery
I have a key that will unlock a puzzling mystery

First, let’s see check with the Stanford University Encyclopedia of Philosophy:

‘Atheism’ means the negation of theism, the denial of the existence of God.

Stanford University is one of the top 5 universities in the United States, so that’s a solid definition. To be an atheist is to be a person who makes the claim that, as a matter of FACT, there is no intelligent agent who created the universe. Atheists think that there is no God, and theists think that there is a God. Both claims are objective claims about the way the world is out there, and so both sides must furnish forth arguments and evidence as to how they are able to know what they are each claiming.

Philosopher William Lane Craig has some thoughts on atheism, atheists and lacking belief in God in this reply to a questioner.

Question:

In my discussions with atheists, they  are using the term that they “lack belief in God”. They claim that this is different from not believing in God or from saying that God does not exist. I’m not sure how to respond to this. It seems to me that its a silly word-play and is logically the same as saying that you do not believe in God.
What would be a good response to this?
Thank you for your time,

Steven

And here is Dr. Craig’s full response:

Your atheist friends are right that there is an important logical difference between believing that there is no God and not believing that there is a God.  Compare my saying, “I believe that there is no gold on Mars” with my saying “I do not believe that there is gold on Mars.”   If I have no opinion on the matter, then I do not believe that there is gold on Mars, and I do not believe that there is no gold on Mars.  There’s a difference between saying, “I do not believe (p)” and “I believe (not-p).”   Logically where you place the negation makes a world of difference.

But where your atheist friends err is in claiming that atheism involves only not believing that there is a God rather than believing that there is no God.

There’s a history behind this.  Certain atheists in the mid-twentieth century were promoting the so-called “presumption of atheism.” At face value, this would appear to be the claim that in the absence of evidence for the existence of God, we should presume that God does not exist.  Atheism is a sort of default position, and the theist bears a special burden of proof with regard to his belief that God exists.

So understood, such an alleged presumption is clearly mistaken.  For the assertion that “There is no God” is just as much a claim to knowledge as is the assertion that “There is a God.”  Therefore, the former assertion requires justification just as the latter does.  It is the agnostic who makes no knowledge claim at all with respect to God’s existence.  He confesses that he doesn’t know whether there is a God or whether there is no God.

But when you look more closely at how protagonists of the presumption of atheism used the term “atheist,” you discover that they were defining the word in a non-standard way, synonymous with “non-theist.”  So understood the term would encompass agnostics and traditional atheists, along with those who think the question meaningless (verificationists).  As Antony Flew confesses,

the word ‘atheist’ has in the present context to be construed in an unusual way.  Nowadays it is normally taken to mean someone who explicitly denies the existence . . . of God . . . But here it has to be understood not positively but negatively, with the originally Greek prefix ‘a-’ being read in this same way in ‘atheist’ as it customarily is in . . . words as ‘amoral’ . . . . In this interpretation an atheist becomes not someone who positively asserts the non-existence of God, but someone who is simply not a theist. (A Companion to Philosophy of Religion, ed. Philip Quinn and Charles Taliaferro [Oxford:  Blackwell, 1997], s.v. “The Presumption of Atheism,” by Antony Flew)

Such a re-definition of the word “atheist” trivializes the claim of the presumption of atheism, for on this definition, atheism ceases to be a view.  It is merely a psychological state which is shared by people who hold various views or no view at all.  On this re-definition, even babies, who hold no opinion at all on the matter, count as atheists!  In fact, our cat Muff counts as an atheist on this definition, since she has (to my knowledge) no belief in God.

One would still require justification in order to know either that God exists or that He does not exist, which is the question we’re really interested in.

So why, you might wonder, would atheists be anxious to so trivialize their position?  Here I agree with you that a deceptive game is being played by many atheists.  If atheism is taken to be a view, namely the view that there is no God, then atheists must shoulder their share of the burden of proof to support this view.  But many atheists admit freely that they cannot sustain such a burden of proof.  So they try to shirk their epistemic responsibility by re-defining atheism so that it is no longer a view but just a psychological condition which as such makes no assertions.  They are really closet agnostics who want to claim the mantle of atheism without shouldering its responsibilities.

This is disingenuous and still leaves us asking, “So is there a God or not?”

So there you have it. We are interested in what both sides know and what reasons and evidence they have to justify their claim to know. We are interested in talking to people who make claims about objective reality, not about themselves, and who then go on to give reasons and evidence to support their claims about objective reality. There are atheists out there that do make an objective claim that God does not exist, and then support that claim with arguments and evidence. Those are good atheists, and we should engage in rational conversations with them. But clearly there are some atheists who are not like that. How should we deal with these “subjective atheists”?

Dealing with subjective atheists

How should theists respond to people who just want to talk about their psychological state? Well, my advice is to avoid them. They are approaching religion irrationally and non-cognitively – like the person who enters a physics class and says “I lack a belief in the gravitational force!”.  When you engage in serious discussions with people about God’s existence, you only care about what people know and what they can show to be true. We don’t care about a person’s psychology.

Dealing with persistent subjective atheists

What happens when you explain all of that to a subjective atheist who continues to insist that you listen to them repeat over and over “I lack a belief in God, I lack a belief in God”? What if you tell them to make the claim that God does not exist, and then support it with arguments and evidence, but instead they keep leaving comments on your blog telling you again and again about their subjective state of mind: “I lack a belief in cupcakes! I lack a belief in icebergs!” What if they keep e-mailing you and threatening to expose you on Twitter for refusing to listen to them, or denounce you via skywriting: “Wintery Knight won’t listen to me! I lack a belief in crickets!”. I think at this point you have to give up and stop talking to such a person.

And that’s why I moderate and filter comments on this blog. There are uneducated people out there with access to the Internet who want attention, but I am not obligated to give it to them. And neither are you. We are not obligated to listen to abusive people who don’t know what they are talking about. I do post comments from objective atheists who make factual claims about the objective world, and who support those claims with arguments and evidence. I am not obligated to post comments from people who refuse to make objective claims or who refuse to support objective claims with arguments and evidence. And I’m not obligated to engage in discussions with them, either.

Related posts

How to respond to an atheist who complains about slavery in the Bible

Lets take a closer look at a puzzle
Lets take a closer look at a puzzle

I often hear atheists going on and on about how the Bible has this evil and that evil. Their favorite one seems to be slavery. Here are three things I say to atheists when they push this objection.

The Bible and slavery

First, you should explain to them what the Bible actually says about slavery. And then tell them about the person responsible for stopping slavery in the UK: a devout evangelical named William Wilberforce.

Here’s an article that works.

Excerpt:

We should compare Hebrew debt-servanthood (many translations render this “slavery”) more fairly to apprentice-like positions to pay off debts — much like the indentured servitude during America’s founding when people worked for approximately 7 years to pay off the debt for their passage to the New World. Then they became free.

In most cases, servanthood was more like a live-inemployee, temporarily embedded within the employer’s household. Even today, teams trade sports players to another team that has an owner, and these players belong to a franchise. This language hardly suggests slavery, but rather a formal contractual agreement to be fulfilled — like in the Old Testament.3

Atheism and moral judgments

Second, inform them that moral values are not rationally grounded on atheism. In an accidental universe, there is no way we ought to be. There is no design for humans that we have to comply with. There are no objective human rights, like the right to liberty (that would block slavery) or the right to life (that would block abortion). Although you may find that most atheists act nicely, the ones who really understand what atheism means and live it out consistently are not so nice.

Famous atheist Richard Dawkins has previously written this:

The total amount of suffering per year in the natural world is beyond all decent contemplation. During the minute that it takes me to compose this sentence, thousands of animals are being eaten alive, many others are running for their lives, whimpering with fear, others are slowly being devoured from within by rasping parasites, thousands of all kinds are dying of starvation, thirst, and disease. It must be so. If there ever is a time of plenty, this very fact will automatically lead to an increase in the population until the natural state of starvation and misery is restored. In a universe of electrons and selfish genes, blind physical forces and genetic replication, some people are going to get hurt, other people are going to get lucky, and you won’t find any rhyme or reason in it, nor any justice. The universe that we observe has precisely the properties we should expect if there is, at bottom, no design, no purpose, no evil, no good, nothing but pitiless indifference.

(“God’s Utility Function,” Scientific American, November, 1995, p. 85)

When atheists like Dawkins talk about morality, you have to understand that they are pretending. To them, morality is just about personal preferences and cultural conventions. They just think that questions of right and wrong are arbitrary. Things that are wrong in one time and place are right in another. Every view is as right as any other, depending on the time and place. That’s atheist morality.

What’s worse than slavery? Abortion!

Third, you should ask the atheist what he has done to oppose abortion. Abortion is worse than slavery, so if they are sincere in thinking that slavery is wrong, then they ought to think that abortion is wrong even more. So ask them what they’ve done to oppose the practice of abortion. That will tell you how sincere they are about slavery.

Here’s atheist Richard Dawkins explaining what he’s done to stop abortion:

That’s right. The head atheist supports killing born children.