 According to (Co+k), the agent’s belief set ought to be closed only under known logical consequence. Let us call this an attitudinally constrained or, more specifically, the epistemically constrained variant of Co+ (whence the “k” in the label). Different authors may go in for different types of attitudes. Knowledge, of course, is a factive attitude. Some will wish to leave room for the possibility of (systematic) logical error. For instance, an agent might mistakenly comply with the principle \(A\supset B, B \models A\). Perhaps even someone with erroneous logical convictions such as this should, for the sake of internal coherence, comply with the principles he deems correct. An agent who sincerely took an erroneous principle to be correct but failed to reason in accordance with it may be seen to manifest a greater degree of irrationality than someone who at least conformed to principles he endorses. But we can also imagine more interesting cases of systematic error. Suppose I am impressed with an argument for a particular non-classical logic as a means of parrying the semantic paradoxes. I thus come to espouse the logic in question and begin to manage my doxastic attitudes accordingly. But now suppose in addition that unbeknownst to me the arguments that persuaded me are not in fact sound. Again, it might be thought that though I am mistaken in my adherence to the logic, so long as I had good reasons to espouse it, it may nevertheless be proper for me to comply with its principles. If logical error in either of these two senses is to be accommodated, the appropriate attitude would have to be non-factive.