The Occult
A true understanding of the modern definition of the occult cannot be separated from an understanding of the philosophical debate over primary and secondary qualities. Simply put, "an 'occult quality' is anything that is deemed to possess an exclusively objective existence, in spite of being imperceptible" (WCT 25).

In current terms, Barfield asks us to remember, "All qualities are occult, inasmuch as they are not accessible to passive sensation alone. There has to be an element of feeling in the perception, which is ruled out by the presuppositions of the scientific method. That is why science has become all quantities" ("IOB" 13).

The sort of acts and/or knowledge customarily thought of as occult (talking with the dead, etc.), these Barfield describes as being like attempts "to botanize, or to cultivate, a love and understanding of nature by investigating fungi." "This is," he adds, "not to condemn it. A loving study of fungi may well throw a special light not only on fungi themselves, but on the whole working of nature in her normal manifestations" (RM 153-54).
 

See in particular "Science and Quality" (RM 176-86).