In a new post on his blog, GatesNotes, billionaire philanthropist and Microsoft founder Bill Gates warned that AI could take over the world.

In the post, Gates recounted an experience he had with AI late last year, when an AI program received the highest possible score on an AP Biology exam.

Gates says that the interaction caused him to reflect on the way AI will change industries, and the Gates foundation, over the next decade.

He explained that AI’s presence could help reduce inequality and inequities in education, and improve outcomes for patients in the medical industry.

He added, “AI will enhance your work – for example by helping with writing emails and managing your inbox,” explaining that AI will improve the efficiency of everyday workers.

But, he added, there are risks. “AIs also make factual mistakes and experience hallucinations.” He said that there is a, “threat posed by humans armed with AI.” and that AI could potentially “decide that humans are a threat, conclude that its interests are different from ours, or simply stop caring about us …”

AI has also raised concerns about privacy and the legal system – and as Gates shows himself, it’s hard to know where to land on the topic between enthusiasm and fear.