"The acceptance of abortion does not end with the killing of unborn human life. It continues on to affect our attitude toward all aspects of human life. This is most obvious in how quickly, following the acceptance of abortion, comes the acceptance of infanticide―the killing of babies who after birth do not come up to someone's standard of life worthy to be lived―and then on to euthanasia of the aged. If human life can be taken before birth, there is no logical reason why human life cannot be taken after birth. If once a man indulges himself in murder, very soon he comes to think little of robbing; and from robbing he comes next to drinking and Sabbath-breaking, and from that to incivility and procrastination. Once begin upon this downward path, you never know where you are to stop. Many a man has dated his ruin from some murder or other that perhaps he thought little of at the time" (39).
This is a small exerpt from Who is for Life? by Francis A. Schaeffer. We can see clearly from this that Schaeffer employs a 'slippery-slope' fallacy. In this example, he draws the conclusion that to be a proponent of abortion is also to be a proponent of countless, less controversial, and clearly morally impermissible actions(i.e. infanticide, murder, etc). A slipper slope argument operates by drawing the deduction that because A, then B... and because Y, Z so because A is true, Z(which is clearly wrong) must also be true. The fallacy in Schaeffer's argument is in the inconsistent, and generally invalid method with which he attempts to display a causation between each of the steps on his slope.