Indeed it is in emphasising exceptions that his own role will largely consist. And above all must he beware of setting up any arbitrary "scientific frontier" between the part of Nature that he knows and the part that he does not know. He can trace the great flood of evolution to the point at which he stands; but a little beyond him it loses itself in the darkness; and though he may realise its general force and direction, and roughly surmise the mode in which its bed will be shaped, he can but dimly picture the scenes through which it will flow.

But if the science of life cannot be final, there is no reason why it should not be accurate and coherent. And if the scope of definite scientific comprehension is here specially restricted, and the unexpected is specially certain to occur, that is no reason for abating one jot of care in the actual work that it remains possible to do - the work of sifting and marshalling evidence, of estimating sources of error, and of strictly adjusting theories to facts. On the contrary, the necessity for such care is only increased. If incaution may be sometimes shown in too peremptorily shutting the door on alleged phenomena which are not in clear continuity with established knowledge, it is far more often and flagrantly shown in the claim for their admission. And it is undeniable that the conditions which have been briefly described expose speculation on the possible developments of vital phenomena to peculiar dangers and difficulties. In proportion as the expert moderates his tone, and makes his forecasts in a tentative and hypothetical manner, it is certain that those who are not experts will wax bold in assertion and theory.

The part of the map that science leaves blank, as terra incognita, is the very one which amateur geographers will fill in according to their fancy, or on the reports of uncritical and untrustworthy explorers. The confidence of ignorance is always pretty accurately adjusted to the confidence of knowledge. Wherever the expert can put his foot down, and assert or deny with assurance, the uninstructed instinctively bow to him. He fearlessly asserts, for instance, that the law of the conservation of energy cannot be broken; the world believes him, and the inventors of perpetual-motion machines gradually die off. But suppose the question is of possible relations of human beings to inanimate things or to one another, new modes of influence, new forms of sensitiveness. Here responsible science can give no confident denial; here, therefore, irresponsible speculation finds its chance. It has, no doubt, modified its language under the influence of half a century of brilliant physical discovery. It takes care to shelter its hypotheses under the name of law: the loosest of philosophers nowadays would hesitate to appeal, as the elder Humboldt appealed sixty years ago, to a " sense of yearning in the human soul," as a proof that the course of nature may suffer exceptions.1 But the change is often rather in name than in fact; the "natural" lends itself to free guessing quite as easily as the "supernatural "; and nowhere in Nature is this freedom so unchartered as in the domain of psychic life.

Speculation here is not only easy; it is, unfortunately, also attractive. The more obscure phenomena and the more doubtful assumptions are just those on which the popular mind most readily fastens; and the popular tongue rejoices in terms of the biggest and vaguest connotation. Something also must be set down to a natural reaction. Even persons whose interest has been earnest and intelligent have found scientific moral hard to preserve, in departments surrendered by a long-standing convention of unscientific treatment. Thus, in their practice, they have come to acquiesce in that surrender, and have dispensed with habits of caution for which no one was likely to give them credit; while in their polemic they have as much resented the stringent demands for evidence, in which their opponents have been right, as the refusal to look at it when it is there, in which their opponents have been wrong.

§ 3. The above facts, and the peculiar obligations which they involve, should never be lost sight of by the serious student of "psychical"² phenomena. His path is one that eminently craves wary walking. On the one hand, he finds new dim vistas of study opening out, in an age whose ideal of scientific studies is formed from the most highly developed specimens of them; and the twilight which has in every class of knowledge preceded the illuminating dawn of law is made doubly dark and dubious for him by the advanced daylight of scientific conceptions from which he peers into it. He finds, moreover, that the marvellous recent extension of the area of the known through additions to its recognised departments and multiplication of their connections, has inevitably and reasonably produced a certain rigidity of scientific attitude - an increased difficulty in breaking loose from association, and admitting a new department on its own independent evidence. And on the other hand, he finds himself more or less in contact with advocates of new departments who ignore the weight of the presumption against them - who fail to see that it is from the recognised departments that the standard of evidence must be drawn, and that if speculation is to make good its right to outrun science, it will certainly not be by impatience of scientific canons.

On this side the position of the psychical student is one in which the student of the recognised sciences is never placed. The physicist never finds his observations confronted or confounded with those of persons who claim familiarity with his subject while ignoring his methods: he never sees his statements and his theories classed or compared with theirs. He is marked out from his neighbours by the very fact of dealing with subject-matter which they do not know how even to begin to talk about. The "psychicist" is not so marked out. His subject matter is in large measure common property, of which the whole world can talk as glibly as he; and the ground which must be broken for science, if at all, by the application of precise treatment, has already been made trite in connection with quite other treatment.

1 Briefe an cine Freundin, p. 61.

² The specific sense which we have given to this word needs apology. But we could find no other convenient term, under which to embrace a group of subjects that lie on or outside the boundaries of recognised science, while seeming to present certain points of connection among themselves. For instance, this book will contain evidences of the relation of telepathy - its main theme - both to mesmerism and to certain phenomena which are often, without adequate evidence, attributed to minds apart from material organisms.