The SLED Test is truly invaluable when trying to persuade and defend your Pro-life views to others. This method was first developed by Stephen Schwarz in his book "The Moral Question of Abortion". It has since been adopted by prominent pro-life writers such as Francis Beckwith, Scott Klusendorf, and Stephen Wagner.

SLED it is an acronym for Size, Level of Development, Environment, and Degree of Dependency.

Whether you are pro-life or pro-choice everyone will agree that a toddler is a valuable human being and has fundamental human rights. The unborn differ from toddlers in only four ways:  Size,  Level of Development,  Environment, and  Degree of Dependency.

• The unborn is smaller a toddler, but toddlers are also smaller than teenagers or adults and yet still human.

• The unborn is less developed than a toddler, but toddlers are less developed than teenagers and adults and yet still human.

• The unborn are still in the womb and therefore in a different location than a toddler, but a toddlers can move to different locations and they are still valuable human beings who still have human rights just like teenagers or adults.

• And last but not least the unborn is more dependent than a toddler, but toddlers are more dependent than a teenager or an adult would be. And many others of various ages depend on other things (i.e. medications, caregivers, machines) to sustain their lives and yet they are all still irrefutably human beings and have immeasurable value and therefore a right to life just like anyone else.

We've just shown that the unborn are exactly like toddlers in all of those four ways. So how do people justify killing the unborn on these same principles, when we protect born humans who have the same deficiencies?


Let's take a further look at these same principles...



Size: It's true that embryos and fetuses are much smaller than a newborn baby or an adult.  And during different stages in their development they might not look like what some would consider a "normal" human being would look like that's true. But at all stages of their development they are still human beings and they look exactly the way that a human being would look at that particular time in their development  They still have the same DNA and genetic makeup as they will when they are an adult. If you took a sample of their DNA and tested it, it would still show that they are in fact a human being. They are just much smaller and still in the normal growth stages of a human being. So how does their size and appearance determine their value or their right to exist? Should a person be able to kill another person because they are a certain size or not? Is a large person any more valuable than a small person? Should a 50 year old woman have the right to say that a 7 year old child doesn't have the right to exist because they are smaller and less developed mentally and physically than an adult? Size does not determine a person's worth or make them any more of a human being than anyone else. Men are usually bigger than women but that doesn't make a man any more important or valuable than a woman is. Neither does size (or their appearance) make an unborn baby any less valuable than a full grown adult. Both are living human beings in different stages of human development and therefore have immeasurable human worth and the right to life just like you or me.


Level of development: Embryos and fetuses are not as developed as an adult but again what difference should this make? A two year old boy is less developed than a 17 year old teenage boy does that make the two year old any less of a human being than the teenager? Should the two year old not be allowed to live because he isn't yet as cognitively intellectual as the teenager? Some people like to argue that a person's capacity for self awareness, their ability to feel pain, and their ability to think logically is what makes a human being truly a "person". If that is true what about people who are in reversible comas who aren't able to think and aren't aware of where they are, do they cease to be a human being because they don't know these things while in the coma? If that is true then a person that is put under general anesthesia for an operation would cease to be a person as well because they can't think, they aren't aware of pain, and they don't know where they are in their in environment while they are under anesthesia? Should a person have a right to kill them? There are people with medical conditions that cause them to not be able to feel physical pain and yet they are still every much a human being as you or I. A person doesn't cease to be a human being because of their age or their ability to think, or know where they are in their environment, or even their level of intelligence at any point. A person's value isn't determined by their abilities or lack there of. Every person no matter their age or size differs in their levels of intelligence, their talents, and abilities to preform certain tasks. And in the degree to which they feel pain (some people naturally have more tolerance for pain than others). If these were the requirements for a human being to be a person then newborn babies and indeed infants up until several months old would not qualify as human beings or persons and would have no value. And many teenagers and adults would not qualify as person's or have the right to life either.

Embryo at 8 weeks

Environment: Where a person is has no bearing on who or what they are. Would your value change because you walked into another room? Or because you drove your car to another state? No? Then how does the distance of eight inches down the birth-canal suddenly change the unborn from a non-human being to a human being? How does that small length of space determine the right to kill that child or not? If the unborn were not already a human being and had value before it was born simply changing it's location by a few inches couldn't make it so. Neither does the unborn human's location in the womb make it any less of a human being than you or I because it is surrounded by amniotic fluid until right before it's birth. That is the normal environment for any human being at that point in his or her development and until it is time for the child to be born.


Along these same lines I have also heard the arguments "It’s Not in the World Yet. It' can't even breathe" so it's not a person. Steve Wagner from Stand to Reason has addressed and refuted these claims beautifully here is what he said: “What do you mean by saying the unborn isn’t ‘in the world’?  Surely the unborn is in the world – it’s simply hidden from view.  It doesn't interact with you and I like a toddler does, but isn’t he interacting with his mother in exactly the way someone at his stage of development should?  It’s interesting that you claim the unborn is not breathing air.  Do you mean that he isn’t even undergoing oxygen exchange, or respiration?  All of us did that from the moment we began to exist as zygotes.  But you must think breathing air into the lungs is critical for value.  What is it about the unborn’s method of respiration or the location of her respiration that diminishes her value?  Let me ask you a question.  How long can you breathe under water?  For about one swallow of water, right?  Well, did you know that the unborn is not only surrounded by amniotic fluid, she is breathing it in and out of her lungs? If you can’t survive in her world, why do you expect her to survive in yours?  Isn’t that a bit arbitrary and unfair?”


Embryo's start to breathe in amniotic fluid as early as 8 weeks in preparation for breathing outside the womb. They also start swallowing amniotic fluid as early as 9 weeks. The unborn's environment and how they breathe does not determine their humanity, their value, or their right to life.



Degree of Dependency: If viability is what makes a human being valuable and gives it the right to exist then anyone who is a diabetic and dependent on insulin to live, or anyone who has kidney failure and needs dialysis to survive are not valuable human beings. Should we be able to kill them because of their degree of dependence on something other than themselves for survival? No of course not. Is a person who is undergoing chemo therapy treatments and might require the assistance of someone with their daily actives for a time any less human because of this? Is an elderly person who requires a caregiver for certain things suddenly of no value and has not right to life? Do conjoined twins who might share the same blood type and certain bodily systems or parts have no value or are in human because of their situation? The answer in all cases is no. Neither is the unborn any less human or of any less value than anyone else because they are dependent upon their mother until it is time for them to be born. But what about the mother it's her body she should have the choice in what she does with her own body. The unborn is not part of the mother's body they are not the same entity. The unborn has a separate body from the mother. Does the mother have 2 heads, two kidneys, four arms and legs, can she have a penis, or does she have four ovaries? No the unborn child is a separate person from the mother. It has it's own body that is not her body and it has the same rights to life and it's body as the mother does to hers.


In all these examples it's been proven that no matter the degree of a person's development, their size, their location, or their degree of dependency they still have immeasurable value. They are human beings and as such have undeniable rights the chief of which is the to life just like you or me. For without the right to life all other rights are meaningless.


Please watch this great video on the Tactics for Pro-Life Persuasion from Alan Shlemon of Stand to Reason.   He shows how to use the SLED test effectively here. He has great tips on how to effectively prove your pro-life beliefs scientifically and in a manner that won't take you all day to prove your points. I highly recommend this video to anyone that is pro-life these tips are truly invaluable! The video is from the 2011 Oregon Right to Life conference.