There is a cautionary tone to Sergey Brin’s annual shareholder letter this year, as the Alphabet president and cofounder shared his thoughts on the company’s services, artificial intelligence (AI) and the ability of AI to help computer systems learn without the need to humans to hard code them.

More than one billion people now use Search, YouTube, Maps, Play, Gmail, Android, and Chrome every month, and artificial intelligence has become the technology behind the scenes powering much of these services.

Search and Gmail are also among the basic services. For each month that “transformative new techniques” and technologies emerge, Brin wrote, “We are truly in a technology renaissance.” And with those transformative technologies comes “greater responsibility for their impact of their work on society.”

Brin began the letter with a passage from Charles Dickens’ A Tale of Two Cities, in which he talks about the “best of times” and “the worst of times,” along with the age of wisdom and foolishness, light and darkness, and hope and despair.

While Brin expressed optimism about the potential of technology to conquer the world’s greatest problems, he cautioned the industry to “tread with deep responsibility, care, and humility” — something that he has not focused upon as much in the past.

Typically he writes about the “awesomeness” of technology and advances, but rarely cautions about its impact on the world and society. This letter had a slightly different tone and sentiment then in past years, almost as if Alphabet will move forward with a more optimistic, yet cautious, approach.

With new opportunities come new responsibilities. The internet and mobile devices have created opportunities and improved the quality of life for billions of people, but Brin finally acknowledged that there are legitimate and pressing issues being raised about the implications and impacts of these advances, including the use of data. 

He also wrote about the collaboration between two of Alphabet’s machine-learning companies — Google Brain and DeepMind — and that the Nest subsidiary officially rejoined Google to create a hardware group.