World-renowned physicist Stephen Hawking is furious, and no, it’s not at someone else with some different theory about how the cosmos works. He’s mad at the UK’s National Health Service, and specifically leadership of the Conservative party who he says is trying to turn it into a replica of the for-profit U.S. health care system.

Hawking’s area of expertise is physics, and he authored the best-selling book “A Brief History of Time,” but he has not been shy about dipping into other matters and using his fame to speak out on issues near and dear to his heart. In a letter published in the Guardian, Hawking, who at 21 was diagnosed with motor neurone disease at age 21, accused Conservatives of pushing Britain into a health care crisis.

He was particularly critical of UK health minister Jeremy Hunt, who he said was cherry-picking evidence to justify the policies his party was putting in place. Hunt responded in kind, slamming Hawking for spreading a “pernicious falsehood.”

Hawking wrote: “The care I have received since being diagnosed with motor neurone disease as a student in 1962 has enabled me to live my life as I want, and to contribute to major advances in our understanding of the universe. … In the U.S., where they are dominant in the healthcare system, these corporations make enormous profits, healthcare is not universal, and it is hugely more expensive for the outcomes patients receive than in the UK,” he added. “We see the balance of power in the UK is with private healthcare companies, and the direction of change is towards a U.S.-style insurance system.”