Some knowledge about hypothermia comes from brutal Nazi medical experiments conducted on prisoners of war. Considering the data came from the destruction of others’ lives, are there ethical issues when modern-day scientists use it? Could it be considered a form of collaboration with the Nazis? Or does the origin of the data matter if the data is useful? Declaring the data off-limits could lead to preventable deaths, while using the data seems coldheartedly clinical. ISAAC MAYER, SAN DIEGO

There are many volatile questions embedded here (including the scientific validity of the Nazis’ experiments, which many researchers have cast doubt upon). But — assuming the data is accurate — I’ll answer the easiest question first: You ask, “Does the origin of the data matter if the data is useful?” The answer is yes. History matters. Motives matter. These have to be part of the discussion. But there’s also an uncomfortable actuality that comes with this particular case: We can’t unlearn what we now know. We can’t decide something is false because we hate the way it was researched. We can’t ignore lifesaving information because someone died in the process. We can’t build a time machine to relearn that same information in a different way. There’s a practical reality here that nullifies a lot of the salient details — this knowledge is real, regardless of how we feel about its derivation.

Let’s say the police suspect a man has committed a murder, but they have no clear grounds for their suspicion. Without a warrant, a rogue cop searches the suspect’s home when the man is away on vacation, finding irrefutable proof that he is the killer. The suspect is arrested and goes to trial. The judge subsequently bars the ill-gotten evidence from the trial on Fourth Amendment grounds, and the man goes free. But this does not mean the murder did not happen. The absence of punishment does not make the event itself disappear.

Our man-made judicial system has laws we collectively agree to be just, but the laws of nature simply exist. Everything about how the Nazis studied hypothermia on prisoners was wrong. The scientists were war criminals. The process was unethical in every conceivable context. Yet the raw information that remains from that travesty is essentially neutral. The temperature where hypothermia begins, the length of time it takes for organs to shut down — these are biological facts. The Nazis’ immorality should be recognized and remembered, but they didn’t invent the data they discovered. A modern-day rescue worker who saves a child who fell through the ice is not complicit with Josef Mengele; he is complicit with the biological imperatives that govern the human body (regardless of who discovered those imperatives first). Now, is that “coldheartedly clinical”? I suppose you could argue that it is. But that’s not the same as being unethical, and it’s certainly not coldhearted to the kid who gets pulled from a freezing river.