The topic of epistemic obligation warrants its own discussion. But for now think of it as the idea that you ought to accept as true that which you have reason to believe is true. In Locke’s phrase, it’s the idea that we ought to “govern our opinion” according to reason.
For he governs his assent right, and places it as he should, who, in any case or matter whatsoever, believes or disbelieves according as reason directs him. He that doth otherwise, transgresses against his own light, and misuses those faculties which were given him to no other end, but to search and follow the clearer evidence and greater probability.
John Locke, quoted in Plantinga, Alvin. Warranted Christian Belief. Oxford University Press, 2000. pp. 86-87.
In other words, it’s a failure of duty to reject as false something you rationally believe to be true or to affirm as true something you rationally believe to be false.
I will be getting into this topic in more detail in future posts, but I wanted lay down this marker first for reference.
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