  Though useful as an ideal, simple conditioning is not widely applicable because it requires the learner to become absolutely certain of E's truth. As Richard Jeffrey has argued (Jeffrey 1987), the evidence we receive is often too vague or ambiguous to justify such "dogmatism."  On more realistic models, the direct effect of a learning experience will be to alter the subjective probability of some proposition without raising it to 1 or lowering it to 0. Experiences of this sort are appropriately modeled by what has come to be called Jeffrey conditioning (though Jeffrey's preferred term is "probability kinematics").