I argue that the core of genuinely academic freedom ought to be freedom in research and teaching, subject to disciplinary standards of expertise. I discuss the law in the United States, Germany, and England, and express doubts about the American view that distinctively academic freedom ought to encompass "extramural" speech on matters of public importance (speakers should be protected from employment repercussions for such speech, but not because of their freedom qua academics). I treat freedom of academic expression as a subset of general freedom of expression, focusing on the Millian argument that freedom of expression maximizes discovery of the truth, one regularly invoked by defenders of academic freedom. Marcuse argued against Mill (in 1965) that "indiscriminate" toleration of expression would not maximize discovery of the truth. I show that Marcuse agreed with Mill that free expression is only truth- and utility-maximizing if certain background conditions obtain: Thus, Mill argues that the British colony in India would be better off with "benevolent despotism" than Millian liberty of expression, given that its inhabitants purportedly lacked the maturity and education requisite for expression to be utility-maximizing. Marcuse agrees with Mill that the background conditions are essential, but has an empirical disagreement with him about what those are and when they obtain: Mill finds them wanting in colonial India, Marcuse finds them wanting in capitalist America. Perhaps surprisingly, Marcuse believes that "indiscriminate" toleration of expression should be the norm governing academic discussions, despite his doubts about the utility-maximizing value of free expression in capitalist America. Why think that? Here is a reason: Where disciplinary standards of expertise govern debate, the discovery of truth really is more likely, but only under conditions of "indiscriminate" freedom of argument, i.e., academic freedom. This freedom is not truly "indiscriminate": Its boundaries are set by disciplinary competence, which raises an additional question I try to address. In sum, the libertarians (Mill and Popper) and the Marxists (Marcuse) can agree that academic freedom is justified, at least when universities are genuine sites of scientific expertise and open debate.