"All fixed, fast-frozen relations, with their train of ancient and venerable prejudices and opinions, are swept away, all new-formed ones become antiquated before they can ossify. All that is solid melts into air, all that is holy is profaned…"

On July 25, 1978, Louise Brown was born in Oldham, England, the first human born through in vitro fertilization, through the work of Patrick Steptoe, a gynecologist, and Robert Edwards, a physiologist. Her birth was greeted with strong (though not universal) expressions of ethical dismay. Yet in 2016, the latest year for which we have data, nearly two percent of the babies born in the United States – and around the same percentage throughout the developed world – were the result of IVF. Few, if any, think of these children as unnatural, monsters, or freaks or of their parents as anything other than fortunate.

How should we view Dr. He today, knowing that the world's eventual verdict on the ethics of biomedical technologies often changes?

On November 25, 2018, news broke that Chinese scientist, Dr. He Jiankui, claimed to have edited the genomes of embryos, two of whom had recently become the new babies, Lulu and Nana. The response was immediate and overwhelmingly negative.

Times change. So do views. How will Dr. He be viewed in 40 years? And, more importantly, how should we view him today, knowing that the world's eventual verdict on the ethics of biomedical technologies often changes? And when what biomedicine can do changes with vertiginous frequency?

How to determine what is and isn't ethical is above my pay grade. I'm a simple law professor – I can't claim any deeper insight into how to live a moral life than the millennia of religious leaders, philosophers, ethicists, and ordinary people trying to do the right thing. But I can point out some ways to think about these questions that may be helpful.

First, consider two different kinds of ethical commands. Some are quite specific – "thou shalt not kill," for example. Others are more general – two of them are "do unto others as you would have done to you" or "seek the greatest good for the greatest number."

Biomedicine in the last two centuries has often surprised us with new possibilities, situations that cultures, religions, and bodies of ethical thought had not previously had to consider, from vaccination to anesthesia for women in labor to genome editing. Sometimes these possibilities will violate important and deeply accepted precepts for a group or a person. The rise of blood transfusions around World War I created new problems for Jehovah's Witnesses, who believe that the Bible prohibits ingesting blood. The 20^th century developments of artificial insemination and IVF both ran afoul of Catholic doctrine prohibiting methods other than "traditional" marital intercourse for conceiving children. If you subscribe to an ethical or moral code that contains prohibitions that modern biomedicine violates, the issue for you is stark – adhere to those beliefs or renounce them.

If the harms seem to outweigh the benefits, it's easy to conclude "this is worrisome."

But many biomedical changes violate no clear moral teachings. Is it ethical or not to edit the DNA of embryos? Not surprisingly, the sacred texts of various religions – few of which were created after, at the latest, the early 19^th century, say nothing specific about this. There may be hints, precedents, leanings that could argue one way or another, but no "commandments." In that case, I recommend, at least as a starting point, asking "what are the likely consequences of these actions?"

Will people be, on balance, harmed or helped by them? "Consequentialist" approaches, of various types, are a vast branch of ethical theories. Personally I find a completely consequentialist approach unacceptable – I could not accept, for example, torturing an innocent child even in order to save many lives. But, in the absence of a clear rule, looking at the consequences is a great place to start. If the harms seem to outweigh the benefits, it's easy to conclude "this is worrisome."

Let's use that starting place to look at a few bioethical issues. IVF, for example, once proven (relatively) safe seems to harm no one and to help many, notably the more than 8 million children worldwide born through IVF since 1978 – and their 16 million parents. On the other hand, giving unknowing, and unconsenting, intellectually disabled children hepatitis A harmed them, for an uncertain gain for science. And freezing the heads of the dead seems unlikely to harm anyone alive (except financially) but it also seems almost certain not to benefit anyone. (Those frozen dead heads are not coming back to life.)

Now let's look at two different kinds of biomedical advances. Some are controversial just because they are new; others are controversial because they cut close to the bone – whether or not they violate pre-established ethical or moral norms, they clearly relate to them.

Consider anesthesia during childbirth. When first used, it was controversial. After all, said critics, in Genesis, the Bible says God told Eve, "I will greatly multiply Your pain in childbirth, In pain you will bring forth children." But it did not clearly prohibit pain relief and from the advent of ether on, anesthesia has been common, though not universal, in childbirth in western societies. The pre-existing ethical precepts were not clear and the consequences weighed heavily in favor of anesthesia. Similarly, vaccination seems to violate no deep moral principle. It was, and for some people, still is just strange, and unnatural. The same was true of IVF initially. Opposition to all of these has faded with time and familiarity. It has not disappeared – some people continue to find moral or philosophical problems with "unnatural" childbirth, vaccination, and IVF – but far fewer.

On the other hand, human embryonic stem cell research touches deeper issues. Human embryos are destroyed to make those stem cells. Reasonable people disagree on the moral status of the human embryo, and the moral weight of its destruction, but it does at least bring into play clear and broadly accepted moral precepts, such as "Thou shalt not kill." So, at the far side of an individual's time, does euthanasia. More exposure to, and familiarity with, these practices will not necessarily lead to broad acceptance as the objections involve more than novelty.

The first is "what would I do?" The second – what should my government, culture, religion allow or forbid?

Finally, all this ethical analysis must work at two levels. The first is "what would I do?" The second – what should my government, culture, religion allow or forbid? There are many things I would not do that I don't think should be banned – because I think other people may reasonably have different views from mine. I would not get cosmetic surgery, but I would not ban it – and will try not to think ill of those who choose it

So, how should we assess the ethics of new biomedical procedures when we know that society's views may change? More specifically, what should we think of He Jiankui's experiment with human babies?

First, look to see whether the procedure in question violates, at least fairly clearly, some rule in your ethical or moral code. If so, your choice may not be difficult. But if the procedure is unmentioned in your moral code, probably because it was inconceivable to the code's creators, examine the consequences of the act.

If the procedure is just novel, and not something that touches on important moral concerns, looking at the likely consequences may be enough for your ethical analysis –though it is always worth remembering that predicting consequences perfectly is impossible and predicting them well is never certain. If it does touch on morally significant issues, you need to think those issues through. The consequences may be important to your conclusions but they may not be determinative.

And, then, if you conclude that it is not ethical from your perspective, you need to take yet another step and consider whether it should be banned for people who do not share your perspective. Sometimes the answer will be yes – that psychopaths may not view murder as immoral does not mean we have to let them kill – but sometimes it will be no.

What does this say about He Jiankui's experiment? I have no qualms in condemning it, unequivocally. The potential risks to the babies grossly outweighed any benefits to them, and to science. And his secret work, against a near universal scientific consensus, privileged his own ethical conclusions without giving anyone else a vote, or even a voice.

But if, in ten or twenty years, genome editing of human embryos is shown to be safe (enough) and it is proposed to be used for good reasons – say, to relieve human suffering that could not be treated in other good ways – and with good consents from those directly involved as well as from the relevant society and government – my answer might well change. Yours may not. Bioethics is a process for approaching questions; it is not a set of universal answers.

This article opened with a quotation from the 1848 Communist Manifesto, referring to the dizzying pace of change from industrialization and modernity. You don't need to be a Marxist to appreciate that sentiment. Change – especially in the biosciences – keeps accelerating. How should we assess the ethics of new biotechnologies? The best we can, with what we know, at the time we inhabit. And, in the face of vast uncertainty, with humility.