It is desirable but not easy to find parallel illustrations of this difference in attitude in other than psychological discussions; but perhaps the following may be pertinent. If the widespread interest in the North Pole were merely that in the possibility of its furnishing the key to the mystery of the northward-turning magnet, and were at once to disappear upon the removal of the mystery, such an interest would be quite parallel to that of the "psychic researcher;" but the interest of the true physicist in any physical phenomenon which in the future may be demonstrated to exist at the North Pole would be a persistent one, and one depending for its value on the illustration thus revealed, not of mystery but of recognized physical principles. Furthermore, be it observed that however valuable may be the physical facts obtainable by a polar expedition, there is no overwhelming obligation resting upon every physicist to desert his laboratory and embark for the farthest north; but that such expeditions are decided by considerations of general interest, expediency, and importance. There is no obligation resting upon the physicist any more than upon the psychologist to make large sacrifices for the pursuit of ill-defined residual phenomena, and certainly not for the refutal of far-fetched theories and suggested supernatural notions. Physicist and psychologist alike contribute most to the advancement of their science by an open-minded but systematic pursuit of definite, significant, and logically fashioned problems.