For thousands of years of western civilization, abortion was generally illegal after “quickening” (the point at about four months into pregnancy when a baby kicks). This tradition can be traced back at least to the Ancient Greeks. In his book “Politics,” Aristotle said that “the line between lawful and unlawful abortion will be marked by the fact of having sensation and being alive.”  Aristotle thus contended that the right to life generally accrues earlier than birth and irrespective of whether the baby is strong enough to survive after birth (i.e. viability). This broad standard of Aristotle leaves plenty of room for special rules and exceptions in order to allow some late abortions for the life of the mother, rape, incest, grave fetal deformity, maiming of the mother, et cetera. 
Quickening usually occurs at least two months before viability. Many people, including myself, advocate drawing a line between lawful and unlawful abortion no later than four months after conception but no earlier than the end of the embryonic stage. This happens to be what the vast majority of people generally believes.  Because the abortion pill RU486 is only effective on an embryo up until the ninth week of pregnancy, I have loudly supported its legalization for many years.
If we are to face facts, we must acknowledge that the human experience does not suddenly begin the moment each of us is born. All medical experience shows that a fetus has sensation (e.g. taste, hearing, touch, smell, and sight). More importantly, a fetus can think, and has been proven to remember things (like the voice of its mother) after it is born. We are all human beings, and as such are not property.
Here are the numbers: over a million abortions are reported each year in the United States, and of these more than 12% occur after the thirteenth week. In other words, there are about 150,000 second trimester abortions in the United States each year. Common reaso…