The subscription-based news industry, the founders speculated, could someday “be much larger than the newspaper business ever was, much like the ride-hailing industry in San Francisco is bigger than the taxi industry was before Lyft and Uber.” These days, Substack’s founders, investors, and marketing materials all have different ways of describing the startup’s mission. Depending on which source you consult, Substack might be “reinventing publishing,” “pioneering a new ‘business model for culture,’ ” or “attempting to build an alternative media economy that gives journalists autonomy.” It is “writers firing their old business model” or “a better future for news.” Substack’s C.E.O., Chris Best, has said that the company’s intention is “to make it so that you could type into this box, and if the things you type are good, you’re going to get rich.” Hamish McKenzie, one of Substack’s co-founders, told me that he sees the company as an alternative to social-media platforms like Facebook and Twitter. “We started Substack because we were fed up about the effects of the social-media diet,” McKenzie said. Substack’s home page now reads, “Take back your mind.”