We hear that distinction in the “no wonders.” As in: “He was run down. No wonder he got the flu.” “She smoked a pack a day. No wonder she got lung cancer.”

And we heard a variation of that theme late last week from Mick Mulvaney, the former South Carolina Congressman and Freedom Caucuser who now heads the Office of Management and Budget—and who, importantly, has been one of the Trump Administration’s key emissaries in the effort to repeal and replace Obamacare.

Mulvaney was speaking at Stanford University’s Leaders in Global Healthcare and Technology forum and was asked to respond to concerns that late-night host Jimmy Kimmel had raised in a moving monologue about his newborn son’s heart surgery. Kimmel had said that while he could afford the cost of that care—which, among other things, included a 21-day stay in the hospital for his prematurely born son—other parents might not be able to do so under a GOP bill that lets states opt out of rules that now govern the coverage of pre-existing conditions. “No parent should have to decide if they can afford to save their child’s life,” said the TV host—a threshold that one Republican Senator dubbed “the Kimmel Test.”

Mulvaney quickly dismissed that concern: “We have plenty of money to deal with that,” he said. “We have plenty of money to provide that safety net so that if you get cancer you don’t end up broke.” But then he added: “That doesn’t mean we should take care of the person who sits at home, eats poorly and gets diabetes.”

Now, I don’t believe in socking a person over one misspoken line. I, myself, am a king of misspeaking. But Mulvaney’s comment is reflective of that widespread and entrenched mindset I mentioned up top: the belief that some people, at least to some extent, deserve the diseases they get. And that’s not only a dangerous mindset, it’s also terribly misinformed.

That’s not to say that those who smoke aren’t doing something self-destructive and stupid. They are. (Smoking substantially increases a person’s risk of getting a number of cancers, heart and lung diseases, and other ailments.)

But with the exception (perhaps) of some infections, human disease, including lung cancer, is rarely “caused” by one (and only one) thing. Rather, it is most often the result of a complex and often random interplay of factors—you might even call it a collision of factors—including our genes, our environment, and our dumb luck.

Take Mulvaney’s example of diabetes. We’ll just assume he’s not referring to type 1 diabetes, in which the immune system mistakenly targets and kills pancreatic cells that release insulin, a hormone needed for cells throughout the body to properly absorb glucose from the bloodstream—or gestational diabetes, which can occur during pregnancy. We’ll figure he means type 2 diabetes, in which the body makes too little insulin or can’t use it effectively.

Some 29 million Americans have some form of diabetes—and an additional 86 million of us (over the age of 20) have prediabetes, meaning that we have higher-than-normal levels of blood sugar. Diabetes is a devastating, progressive disease that costs the country, by one estimate, nearly $250 billion in medical costs, lost wages, and productivity each year.

It’s also a complicated pathology—with surprising correlations and no straightforward, true-or-false etiology. No singular molecular glitch seems to lie at its heart. While there is a strong heritable factor in the disease, it’s not yet certain which combination of genetic aberrations trigger the disease—or cause it, in the words of one authority, after being “expressed only under the appropriate environmental insults.”

A slew of studies now link diabetes, in various ways, with tuberculosis, Alzheimer’s (which one Japanese research group now suggests may be a “diabetic disorder of the brain”), neural tube defects, glioma, and more. Part of these linkages may be due to diabetes’ myriad effects on (and damage to) the body as it progresses. But there may be other, more deeply rooted, connections—tracing to an overlooked intersection of gene interactions or to another surprise crossing of molecular pathways.

More and more, researchers are discovering unlikely networks of connections between seemingly far-flung diseases and disorders. Sometimes, they show up as a comorbidity—unearthed, perhaps, after a big-data analysis of insurance claims. One Austrian research group, for instance, found highly significant associations between diabetes and 123 separate diseases.

Genes for deafness, meanwhile, are linked with one or more of the genes associated with at least twenty other ailments. And study after study suggests that poor dental health can lead to heart attacks and to vascular disease generally.

With such little-understood connections between diseases and their origin—and between one pathological breakdown and another—it’s an awfully slippery slope to deny health coverage to someone “who sits at home, eats poorly” and gets sick.

The “no wonder” game, in truth, has no end. With this mindset, it’s all too easy to say: “No wonder he got a heart attack. He never flossed.”

This essay appears in today’s edition of the Fortune Brainstorm Health Daily. Get it delivered straight to your inbox.