Suppose that you have only moments to make a case for the lives of the unborn with an unchurched friend. If your friend rejects the authority of Scripture to make this argument, is your case hopeless? Not at all. You can defend biblical truth on abortion using rational arguments that even a secular person can accept.

Pro-life advocates contend that elective abortion unjustly takes the life of a defenseless human being. This simplifies the abortion controversy by focusing attention on just one question: Is the unborn a member of the human family? If so, killing him or her to benefit others is a serious moral wrong. Conversely, if the unborn are not human, elective abortion requires no more justification than having a tooth pulled.

Scientifically, we know that from the earliest stages of development, the unborn are distinct, living, and whole human beings. Leading embryology books confirm this. Prior to advocating abortion, former Planned Parenthood president Alan Guttmacher was perplexed that anyone, much less a medical doctor, would question these basic scientific facts. “This all seems so simple and evident that it is difficult to picture a time when it wasn’t part of the common knowledge,” he wrote in his book Life in the Making.

Philosophically, there is no morally significant difference between the embryo you once were and the adult you are today. Differences of size, stage of development, environment, and degree of dependency are not relevant in the way that abortion advocates need them to be. Harvard-educated philosopher Stephen Schwarz suggests that the simple acronym SLED can be used to illustrate these non-essential differences.

Size: True, embryos are smaller than newborns and adults, but why is that relevant? Do we really want to say that large people are more human than small ones? Men are generally larger than women, but that doesn’t mean they deserve more rights. Size doesn’t equal value.

Level of development: True, embryos and fetuses are less developed than we are. But again, why is this relevant? Four-year-olds are less developed than fourteen-year-olds. Should older children have more rights than younger ones? Some say that self-awareness makes one human. But if that is true, newborns do not qualify as valuable human beings. Remember: Six-week-old infants lack the immediate capacity to perform human mental functions, as do the reversibly comatose, the sleeping, and Alzheimer’s sufferers.

Environment: Where you are has no bearing on who you are. Does your value change when you cross the street or roll over in bed? If not, how can a journey of eight inches down the birth canal suddenly change the essential nature of the unborn from non-human to human? If the unborn are not already human, merely changing their location can’t make them valuable.

Degree of Dependency: If viability makes us human, then diabetics who depend on insulin are not valuable and we may kill them. Conjoined twins who share blood and bodily systems also have no right to life.

In short, it’s far more reasonable to argue that although humans differ immensely with respect to talents, accomplishments, and degrees of development, they are nonetheless equal because they all have the same human nature.

There you have it: a pro-life case that will resonate with secular listeners AND save lives.

Scott Klusendorf is president of Life Training Institute. Get his free training articles at www.prolifetraining.com.