 Of course, it is at least in theory possible to engage in argumentation with oneself along these lines, solitarily weighing the pros and cons of a position. But a number of philosophers, most notably John Stuart Mill, maintain that interpersonal argumentative situations, involving people who truly disagree with each other, work best to realize the epistemic potential of argumentation to improve our beliefs (a point he developed in On Liberty (1859; see entry on  John Stuart Mill).  When our ideas are challenged by engagement with those who disagree with us, we are forced to consider our own beliefs more thoroughly and critically. The result is that the remaining beliefs, those that have survived critical challenge, will be better grounded than those we held before such encounters. Dissenters thus force us to stay epistemically alert instead of becoming too comfortable with existing, entrenched beliefs. On this conception, arguers cooperate with each other precisely by being adversarial, i.e., by adopting a critical stance towards the positions one disagrees with.