What would America’s abortion policy be if the number of months in the gestation of a human infant were a prime number — say, seven or 11? This thought experiment is germane to why the abortion issue has been politically toxic, and points to a path toward a less bitter debate. The House of Representatives has for a third time stepped onto this path. Senate Democrats will, for a third time, block this path when Majority Leader Mitch McConnell brings the House bill to the floor, allowing Democrats to demonstrate their extremism and aversion to bipartisan compromise.

Democracy, which properly is government by persuasion rather than majority bullying or executive or judicial policy fiats, is a search for splittable differences. Abortion, which supposedly is the archetypal issue that confounds efforts at compromise, has for two generations — since the Supreme Court seized custody of the issue in 1973 — damaged political civility.

Pro-abortion absolutists — meaning those completely content with the post-1973 regime of essentially unrestricted abortion-on-demand at any point in pregnancy — are disproportionately Democrats who, they say, constitute the Party of Science. They are aghast that the Department of Health and Human Services now refers to protecting people at “every stage of life, beginning at conception.” This, however, is elementary biology, not abstruse theology: Something living begins then — this is why it is called conception. And absent a natural malfunction or intentional intervention (abortion), conception results in a human birth.

In 1973, the court decreed — without basis in the Constitution’s text, structure or history, or in embryology or other science — a trimester policy. It postulated, without a scintilla of reasoning, moral and constitutional significance in the banal convenience that nine is divisible by three. The court decided that the right to abortion becomes a trifle less than absolute — in practice, not discernibly less — when the fetus reaches viability, meaning the ability to survive outside the womb. The court stipulated that viability arrived at 24 to 28 weeks.

On Oct. 3, the House passed (237-189) the Pain-Capable Unborn Child Protection Act banning abortions (with the usual exceptions concerning rape, incest and the life of the mother) after the 20th week. The act’s supposition is that by then the fetus will feel pain when experiencing the violence of being aborted, and that this matters. Of course, pro-abortion absolutists consider the phrase “unborn child” oxymoronic, believing that from conception until the instant of delivery, the pre-born infant is mere “fetal material,” as devoid of moral significance as would be a tumor in the (if they will pardon the provocative expression) mother.

Whether a 20-week fetus has neurological pathways sufficient for feeling pain is surely a question that science can answer, if it has not already. Already there are myriad intrauterine medical procedures, some involving anesthesia: Doctors can heal lives that America’s extremely permissive abortion law says can be terminated with impunity. Only seven nations allow unrestricted abortion after 20 weeks. Most European nations restrict abortions by at least week 13. France and Germany are very restrictive after 12, Sweden after 18.

Getting a scientific answer to the pain question, even if it is “yes,” should gratify the Party of Science. If the answer is “yes,” those who think fetal suffering is irrelevant can explain why they do.

New medical technologies and techniques are lowering the age of viability. And increasingly vivid sonograms, showing beating hearts and moving fingers, make it increasingly difficult to argue that the “fetal material” is at no point, in any way, a baby. Science is presenting inconvenient truths to the Party of Science, truths that are the reasons the percentage of pregnancies aborted is the smallest since 1973.

In 1973, the court bizarrely called the fetus “potential life”; it is, of course, undeniably alive and biologically human. A large American majority is undogmatic, because uncertain, about — and the House bill does not address — the question of when the living thing that begins at conception should be held to acquire personhood protectable by law. This majority’s commonsensical, prudently imprecise, split-the-difference answer is: Not at conception but well before completed gestation. Hence this majority, its vocabulary provided by the court’s arbitrary jurisprudence, thinks first-trimester abortions (more than 90 percent of abortions) should be legal. After which, approximately a two-thirds majority supports restricting abortions.

When — the sooner the better — the House bill comes to the Senate floor, Democrats will prevent a vote on it. This will be a tutorial on the actual extremists in our cultural conflicts.

© 2017, Washington Post Writers Group