An important task for one who wishes to have a satisfying, coherent worldview, is to explain why other people do not share one's worldview. If intelligent, good, educated, and well-informed people reject one's worldview, and are unmoved by the arguments or reasons one cites for one's worldview, it is natural that one begin to doubt that one's arguments or reasons are persuasive; unless one can come up with a satisfying explanation for how the relevant persons might remain unmoved, despite their intelligence, goodness, education, and cognizance. In short, one will want error theories, or accounts that allow one to synthesize the appearances as experienced by one's opponents, with the truth of one's own worldview.
We may classify error theories as surface, shallow, and deep. A surface error theory is one wherein one simply makes some generalized accusation against the other person, without clearly, explicitly linking it to the propositions, arguments, or reasons that are being offered: "You are a bad person, and that is why you believe this!" In other words, one denies that the other person is in fact intelligent, good, educated, or well-informed. On this point: we are thus very good at catching minor faults in others ("You slightly misrepresented my position!") and we often use this to rationalize why the other person disagrees with us, and to sooth our doubts; all of which is almost always unproductive and uncivil, I suspect, and to be avoided. (Really, this is almost not so much a theory so much as a claim: "The other person is ignorant, bad, or somehow malfunctioning." We assume, rightly, that these might serve as good explanations as to why the other person disagrees with us; but we do not see why.)
A shallow error theory is a more nuanced explanation that tries to not only state, but make intelligible why someone believes something false; to draw out the connection between their badness, ignorance, or malfunctioning, and their error: "They believe in X, because they are committed to Y for dubious motive Z, and X is not compatible with Y." These theories are characterized by being accessible, and by not tending to require substantive commitments to any particular theory of the mind, the world, or the good.
A deep error theory is a more nuanced explanation that tries to make intelligible why someone believes something false, in light of a substantive theory of the mind, the world, or the good: "They believe in X because this mental faculty of theirs, which has function Y, is malfunctioning because of Z, and we could not have known about this, or explained it clearly, except for my theory of the mind, the world, or the good, which says ABC."