While mediumship is not equivalent to Spiritism, it does play an integral role in the teachings and practice of the doctrine.  Though discarnate spirits of the spirit realm have interacted and communicated with human beings throughout history, as evidenced in the records of many cultures and in several religions, it was through a surge of physical mediumship in the mid-19th century that modern spiritualists first became aware of the existence of spirits (i.e. the continuity of life after death) and our ability to communicate with them.  

Later, it was through mediums and intellectual mediumship that the higher spirits were able to work with Allan Kardec and other collaborators to codify Spiritism.

Today, it is also through mediumship that we continue to receive valuable instruction from our spiritual benefactors and carry out fraternal tasks of spiritual healings and treatments.  This is done in cooperation with our partners in the spiritual realm to benefit incarnate and discarnate spirits in need of guidance, education, and consolation.