Here are some quotes from "How We Think" by John Dewey. These quotes deal with the subject of epistemology and how sloppy thinking comes about.
Dependence on others
The first is of those who seldom reason at all, but do and think according to the example of others, whether parents, neighbors, ministers, or who else they are pleased to make choice of to have an implicit faith in, for the saving of themselves the pains and troubles of thinking and examining for themselves.
Self-interest
This kind is of those who put passion [emotion] in the place of reason, and being resolved that shall govern their actions and arguments, neither use their own, nor hearken to other people's reason, any farther than it suits their humor, interest, or party.
Circumscribed experience
The third sort is of those who readily and sincerely follow reason, but for want of having that which one may call large, sound, roundabout sense, have not a full view of all that relates to the question ... They converse but with one sort of men, they read but one sort of book, they will not come in the hearing but of one sort of notions...They have a pretty traffic with known correspondents in some little creek but will not venture out into the great ocean of knowledge.
Effect of dogmatic principles
That which is inconsistent with our principles is so far from passing for probable with us that it will not be allowed possible. The reverence borne to these principles is so great, and their authority so paramount to all other, that the testimony, not only of other men, but the evidence of our own senses are often rejected, when they offer to vouch anything contrary to these established rules ... from their parents, nurses, or those about them; which being insinuated in their unwary as well as unbiased understandings, and fastened by degrees, are at last riveted there by long custom and education, beyond all possibility of being pulled out again. For men, when they are grown up, reflecting upon their opinions and finding those of this sort to be as ancient in their minds as their very memories, not having observed their early insinuation, nor by what means they got them, they are apt to reverence them as sacred things, and not to suffer them to be profaned, touched, or questioned.
Of closed minds
Secondly, next to these are men whose understandings are cast into a mold, and fashioned just to the size of a received hypothesis.
