The Scientific Studies of Spiritism are in many ways similar to those of traditional science. Just as they began with Kardec, they continue to follow, in many ways, the well known "Scientific Method" from Galileo and Newton: an observation of something that is happening; a hypothesis or a preliminary explanation, experimentation with repetition of the phenomena to test the hypothesis an, an analysis and comparison of the results of each repetition, followed by law and theory. 

However, as noted by Kardec, Spiritism, at the same time forms a distinct scientific field, differing from the exact sciences, because, as Kardec wrote, Spiritist (or mediumistic) phenomena "must be observed in passing. It is through a long, careful observation that one discovers the proofs that escape the first glance, especially when one is unfamiliar with the conditions required to produce the phenomena or when one has prejudged them." 

Why is that? It is because the object of study is Spirits! -- who are merely the souls of men! And just like each of us, they have their own thoughts, desires, and intentions. Therefore, the mediumistic phenomena can not be produced at will.  No one can force the spirit under observation to do or say anything unless they want to, and only WHEN they chose to do so. This is very different from the exact sciences where you can test your hypothesis by repeating a phenomena at will, and as many times as you wish. Not only that, but each discarnate spirit, just like the incarnate, is at its own level of advancement and knowledge, adding to the variety of data collected and in need of careful scrutiny 

Critics and skeptics of Kardec's time would often go to him, full of doubts and accusations about the kinds of mediumistic studies that he was involved in and the work that he published as a result of them. And they would tell him, "Ok let me come to one of your meetings to see it for myself and you can prove to me that you speak of the truth." And Kardec would respond, explaining that simply attending a meeting or two would not prove anything or leave the person with a complete knowledge of Spiritism. He said, "You can not take a course in Experimental Spiritism,  and he compared the observation that he did to that of a naturalist observing an animal. 

It is only with time and patience that you will acquire accurate data. He told those who were truly interested to begin first by studying theory and philosophy. Then with a background on the subject, and if they were read to treat the subject in a serious nature, they could attend a meeting and observe the phenomena. Kardec's words hold true today for us as well. Before we involve ourselves in any mediumistic studies, we should study the theories and explanation of the doctrine first. 

Spiritism and Science complete one another.  As Kardec said, "Science, without Spiritism, finds itself unable to explain certain phenomena, simply by the material laws; Spiritism, without Science, would be without support and examination."  

Kardec, Allan. Christian Spiritism (a compilation of two Kardec books: Spiritism Reduced to Its Simplest Expression and What is Spiritism).  Trans. Allan Kardec Educational Society (translated from original French editions, published 1860 and 1859, respectively). Philadelphia, PA. Allan Kardec Educational Society. 1985. 40-41;55; 63;93..

Barbosa, Pedro Franco. "O Espiritismo Cientifico" [Scientific Spiritism] Espiritismo Basico [Basic Spiritism]. 3rd ed. Rio de Janeiro-RJ, Brazil: Federação Espírita Brasileira [Brazilian Spiritist Federation].1987. 103-107.