Principles of epistemic logic I: Knowledge

All epistemic logics come with some idealizations. Not all such idealizations seem acceptable. A large family of epistemic logics assume that if ⌜φ‎⌝ and ⌜ψ‎⌝ are logically equivalent, so are ⌜One knows that φ‎⌝ and ⌜One knows that ψ‎⌝. This assumption, characteristic of normal epistemic logics but also of many non-normal ones, is acceptable only if the objects of knowledge can be construed as sets of possible worlds known under some mode of presentation or other, where knowledge-ascriptions do not yet make those modes explicit. Unlike fine-grained conceptions that reject the assumption, such coarse-grained conceptions of the objects of knowledge have the untoward consequence that failures of logical omniscience are no longer expressible in the logic. But even on coarse-grained conceptions, epistemic logic cannot be expected to be normal. Fine-grained conceptions allow for failures of logical omniscience to be expressible in the logic. On balance, fine-grained conceptions are to be preferred. Against this backdrop, candidate principles for inclusion in the logic of knowledge are critically reviewed in the light of general epistemological considerations. Very few survive closer scrutiny.

Intraoperative MR-Guided Instillation of Phosphorum-32 for Cystic Craniopharyngiomas: Case Report

Intraoperative magnetic resonance imaging has been applied to a number of neurosurgical disease processes since the late 1990's. The ability to visualize the operative site in near-real time has added a significant degree of safety to the treatment of lesions such as a cystic craniopharyngioma which can be located in regions of the brain where an untoward consequence can result in significant neurological morbidity. Previous surgical techniques, although often successful, did not allow the neurosurgeon to directly visualize whether the goals of surgery had been met or whether there was an inadvertent complication associated with the surgical approach until after the event had occurred. The safe and accurate instillation of radioactive phosphorus into this cystic tumor resulted in clinical improvement and the maintenance of normal pituitary function for this patient. The extreme accuracy and safety of this surgical technique is demonstrated by the imaging examples provided.