ANSWER: In modern usage it has a good meaning, as it originally had among the Greeks. Take it to pieces and you will And it means en Theos, in God, denoting inspiration. But it soon began to take on the meaning of fanatic, in which sense Wesley used it. Isaac Taylor, in his Natural History of Enthusiasm, says: "A fanatic is an enthusiast transformed or developed. A typical enthusiast has a warm imagination and a sensitive heart with the malignant element still latent." He lives for only one object, and when opposed the evil is apt to become aroused; then he ceases to be an enthusiast and becomes a fanatic, wild, extravagant and unteachable in his religious opinions. He is infallible, being directly inspired by the Holy Ghost, as he imagines. He thinks every thought is from God and that he has no need of the Bible. "Why do I need a guide-board," I heard a fanatic say in a pulpit, "when I have the Guide?" Another boasted that he had not looked in the Bible during a month. The devil easily trips such people up by injecting temptations to evil acts which, not being tested by the Scriptures, are supposed to be right because inspired by God. This is the road to ruin, trodden by many who were once earnest Christians. Wesley cut off sixty fanatics from his Foundry Society in one day. They called him "poor blind John." Beware of fanaticism, the devil's trap for those whom he can catch in no other way.
— Steele's Answers pp. 194, 195.