54. Mediums display a wide variety in their aptitudes, which render them more suitable or less so for obtaining this or that phenomenon, or this or that type of communication. According to such aptitudes, we may say that there are physical effects, intelligent communications, seeing, speaking, hearing, sensitive, drawing, polyglot, poetic, musical, writing, etc. mediums. A medium cannot expect what is outside his or her faculty. Without understanding the various mediumistic aptitudes, the observer cannot be informed about certain difficulties or impossibilities that may be encountered in the practice of mediumship.
55. Physical effects mediums are most particularly capable of inducing material phenomena, such as movements, raps, etc., with the aid of tables or other objects. When these phenomena express a thought or obey a will, they are intelligent effects, which for that very reason, point to an intelligent cause and are a way for spirits to manifest. By means of a. number of ordinary raps, we may receive answers such as yes or no, or die designation of letters of the alphabet that may be used to form words or sentences. This primitive method is very slow and does not lend itself to lengthy exchanges. Talking tables began the science; nowadays, there are means of communication that are as fast and complete as the ones used between incarnates; tables serve only incidentally and for experimentation.
56. Of all the means of communication, writing is the simplest, fastest and most convenient, and allows the lengthiest exchanges; it is also the faculty most frequently found among mediums.
57. In order to obtain a written communication, physical intermediaries such as baskets, planchettes, etc. attached to a pencil were used at first. It was later realized, that such accessories were needless and that mediums could write directly with the hand as in ordinary circumstances.
58. Mediums write under the influence of the spirits who use them, as their instruments; their hand is caused to write by involuntary movement, which most of the time they cannot control. Some mediums have no awareness ofwhat they are writing; others are vaguely aware, although the thought is not their own. This is what distinguishes the mechanical, intuitive and semi-mechanical mediums. Spiritist science explains the way the spirit's thought is transmitted to the medium and the role the latter plays in communications.
59. Mediums possess the faculty of communication, but effective communication depends on the will of spirits. If spirits do not want to manifest, mediums obtain nothing and are like instruments without musicians.
Spirits communicate only when they want to or when they are able to, and are not at anyone's beck and call; no medium has the ability to make them come whenever desired and against their will.
This explains the intermittence of the faculty in the best mediums, in addition to its suspension, which they sometimes must bear for several months.
Consequently, it would be erroneous to liken mediumship to a talent. Talents are acquired by work, and those who possess them are always master over them; mediums are never master of their faculty, because it depends on an outside will.
60. Physical effects mediums who on a regular basis and at their pleasure are able to obtain certain phenomena - if it does not involve trickery - are being used by low order spirits who enjoy putting on such exhibitions and who were perhaps involved in the same type of work when they were alive. Nevertheless, it would be absurd to believe that even such low order spirits would enjoy being put on display.
61. The darkness required for the production of certain physical effects of course arouses suspicion, but proves nothing against their reality. In chemistry it is a known fact that there are combinations that cannot occur under light, and that compositions and decompositions occur under the action of the luminous fluid. Since all spirit phenomena result from the combination of the personal fluids of both the spirit and the medium, and since these fluids are physical, it should come as no surprise that in certain cases the luminous fluid works against their combination.
62. Intelligent communications also occur by means of the fluidic action of the spirit upon the medium; the fluid of the latter must identify with the fluid of the former. The ease of the communication depends on the degree oilaffinity between the two fluids. Each medium is thus capable of receiving the impression or impulse of this or that spirit's thought to varying degrees. Such a medium may be a good instrument for one, but a bad instrument for another. The result is that even though two equally well- endowed mediums may be right next to each other, a spirit may manifest through one and not the other.
63. Therefore, it is a mistake to believe that it is enough simply to be a medium in order to receive communications from every spirit with the same ease. There are no more universal mediums for making evocations than there is a universal aptitude for inducing every type of phenomenon. Spirits prefer to look for instruments who vibrate in unison with them; if they were to impose themselves on the first to come along, it would be like forcing a pianist to play the violin, under the reasoning that if he or she knows music, he or she should be able to play every instrument.
64. Without harmony - the only quality that can lead to fluidic assimilation - communications are impossible, incomplete or false. They may be false because, in the absence of the spirit desired, there is no lack of others who are ready and willing to take advantage of the occasion to manifest, and who care very little about telling the truth.
65. The fluidic assimilation is at times completely impossible between certain spirits and mediums. At other times - and this is the most common case - it is only established gradually over time. This is what explains why spirits who are accustomed to manifesting through one particular medium do so more easily and why the first manifestations nearly always display a certain restraint and are less explicit.
66. Fluidic assimilation is as necessary in communications involving typtology as it is in those involving writing, since in either case there is a transmission of the spirit's thought, whatever the material means employed.
67. Since mediums cannot impose themselves on the spirit they want to evoke, it behooves the spirit itself to choose its own instrument. In any case, the medium must identify beforehand with the spirit through concentration and prayer, at least for a few minutes, and even for a few days, if possible, in order to induce and activate the fluidic assimilation. This is the way to attenuate the difficulty.
68. Whenever the fluidic conditions are not proper for the spirit to communicate directly with the medium, the communication may occur through the intermediary of the latter s spirit guide. In this case, the thought only arrives second hand; that is, after having passed through two sources. Thus, one can understand how important it is for the medium to be well assisted because if he or she is assisted by an obsessor, ignorant or proud spirit, the communication will inevitably be altered.
Here, the medium's personal qualities truly perform an important role due to the nature of the spirits he or she attracts. The most unworthy mediums can possess powerful faculties, but the safest are those who combine such strength with the best affinities in the spirit world. Now, these affinities are in no way guaranteed by the impressive names that spirits might use or that they might take when signing communications, but by the consistently good nature of the communications obtained from them.
69. Whatever the mode of communication may be, the practice of Spiritism from the experimental point of view entails many difficulties and is not without its problems for anyone who lacks the necessary experience. Whether one is experimenting for oneself or whether simply observing, it is crucial to know how to distinguish amongst the various natures of the spirits that can manifest, to know the causes of all the phenomena, the conditions in which they may be produced, and the obstacles that may be encountered, in order not to ask the impossible. And it is no less necessary to know about all the conditions and all the dangers of mediumship, the influence of the environment, moral dispositions, etc.