Humanism has had many incarnations over the years with most modern humanist societies requiring members to eschew any superstitious, spiritualist or religious beliefs. From Wikipedia:
Isaac Asimov wrote in one of his Black Widower's stories that "supernatural" literally means outside of or above nature. Nature as referenced by this word means the world (or in more modern terms, the universe) in its entirety. Asimov's argument was that since nothing can exist outside nature nothing can be supernatural. If a renaissance style humanist who also happened to have spiritualist beliefs bought into Asimov's definition of "supernatural" then this humanist could sign either of these declarations confident in the knowledge that his belief in the value of seances doesn't qualify as supernatural because nothing is supernatural.
AHA's definition of Humanism
The AHA's definition from its website:
"Humanism is a progressive lifestance that, without supernaturalism, affirms our ability and responsibility to lead ethical lives of personal fulfillment that aspire to the greater good of humanity." Humanism and Its Aspirations
[edit] IHEU's minimum statement on Humanism
All member organisations of the IHEU are required by IHEU bylaw 5.1 to accept[4] the IHEU Minimum statement on Humanism:
Humanism is a democratic and ethical life stance, which affirms that human beings have the right and responsibility to give meaning and shape to their own lives. It stands for the building of a more humane society through an ethic based on human and other natural values in the spirit of reason and free inquiry through human capabilities. It is not theistic, and it does not accept supernatural views of reality.[5]
Isaac Asimov wrote in one of his Black Widower's stories that "supernatural" literally means outside of or above nature. Nature as referenced by this word means the world (or in more modern terms, the universe) in its entirety. Asimov's argument was that since nothing can exist outside nature nothing can be supernatural. If a renaissance style humanist who also happened to have spiritualist beliefs bought into Asimov's definition of "supernatural" then this humanist could sign either of these declarations confident in the knowledge that his belief in the value of seances doesn't qualify as supernatural because nothing is supernatural.