Another cause of error which requires pointing out is fatigue on the part of the experimenters. Every phenomenon which is produced after a long period of waiting stands many chances of being badly observed. The attention kept for a long time on the qui vive becomes weary, gives place to abstraction, and often the phenomena takes the experimenters by surprise; hence they are unable to examine the conditions with certitude. It is also bad to hold very long seances, fatigue quickly setting in.
Such are the principal causes of positive errors; that is to say, of errors tending to persuade one of the existence of an imaginary fact; negative errors, that is to say, those which tend to make one look upon a real fact as an imaginary one, are not less dangerous than positive errors.
In the first place, parti pris is to be pointed out. If we wish to experiment with success, we must experiment without credulity, without faith, even without confidence; but we must not be determined only to meet with fraud.
We must not experiment naïvely. If, at the beginning of a seance, it be useful to allow freedom in order to put the force en train, as Ochorowicz wisely recommends, once the phenomena are established, we must control them with the greatest care. But we should make our intentions known to the medium and to the personification. This, I think, is an indispensable precaution. The personification will always consent to it; but this does not mean we will always obtain the wished-for result. We must not allow the medium or the personification to think we are their dupes if they fraud; we must tell them, gently but clearly, that they are not giving anything good. Equivocation is to be carefully avoided, all misunderstanding is to be shunned.
We must not, however, place the medium under such conditions that the experiment cannot be realised. We do not understand these conditions, and, perhaps, apparently simple phenomena may not be realisable. I remember that at Choisy in 1896, a lady, a member of my family—she has an insurmountable bias against psychical experiments, which she declares a priori are fraudulent—declared to Eusapia that she would believe in her phenomena, if she could make a doll’s table move before her eyes. Eusapia placed this small table on top of the seance-table, but did not succeed in making it move. Why could not such an apparently simple phenomenon be obtained?
We must, therefore, observe, but we must not wish to impose beforehand the conditions which the phenomenon should fulfil in order to be accepted.
Many experimenters tie up the medium, put him into a sack, and seal him therein. If he consents to this, well and good; if he refuses, other means of control must be found. We must not indeed suppose that the medium’s refusal is always due to a desire to fraud. The slightest fetters may sometimes be very painful, especially when there be cutaneous hyperæsthesia.
Before bringing a negative judgment to bear upon the phenomena, the experimenters should always hold a certain number of seances, and should not found their judgment upon one bad seance alone; by so doing they would expose themselves to a wrong course of action.
It is especially in psychical experimentation that inexhaustible patience is necessary.