Epilepsy is related to the electrical activity in the brain and is associated with the balance between the triggering of electrical activity and the limiting of it.
Some children are born with it. Some people develop it after a head injury (which is the most common for cause for young adults) or illness. People who are older (middle aged) when they develop may have strokes or tumors that cause it; and since people who are over 65 can suffer injuries more than younger people, this is yet another cause of Epilepsy.
The cause of Epilepsy is not known in all cases, but not knowing the exact cause of a disorder that involves the process of triggering or limiting electrical activity in the brain doesn't mean doctors don't understand what's happening when a person with Epilepsy of unknown causes develops it.
Throughout history lack of understanding of science has resulted in people believing one medical condition or another has been caused by "bewitching". People who understand the scientific explanation behind medical conditions don't generally believe in "bewitching". An example of a related situation is that through history people believed to be witches were murdered because nobody knew the cause of hallucinations and other "odd" behavior. Today science knows that the cause of behavior/illness that led people of earlier times to believe people were "possessed" was weather changes that meant rye crops developed toxic molds. What a misguided thing it is that in 2010, with all the scientific information available to people, anyone would ever suspect that a person suffering from Epilepsy might be "bewitched". I knew of a young girl who had been beaten and injured as a child and who developed seizures. I also know a young man who suffered mild brain damage (that resulted in a "mild" case of Cerebral Palsy that affects one of his arms and one leg) during birth and who has occasional seizures. What a sad thing it is for people like this to live in a world where anyone might even wonder if they have been "bewitched".