Noun
One moved or actuated by enthusiasm; as: (a) One who imagines himself divinely inspired, or possessed of some special revelation; a religious madman; a fanatic. (b) One whose mind is wholly possessed and heated by what engages it; one who is influenced by a peculiar; fervor of mind; an ardent and imaginative person.
Source: Webster's dictionaryA creator needs only one enthusiast to justify him. Man Ray
No wild enthusiast ever yet could rest, till half mankind were, like himself, possest. William Cowper
The essayist ... can pull on any sort of shirt, be any sort of person, according to his mood or his subject matter philosopher, scold, jester, raconteur, confidant, pundit, devil's advocate, enthusiast. E. B. White
Asceticism is the trifling of an enthusiast with his power, a puerile coquetting with his selfishness or his vanity, in the absence of any sufficiently great object to employ the first or overcome the last. Florence Nightingale
A system needs to be alive and workable even when other people than the first enthusiasts start using it. Reinvention and revolution are enthusiast stuff. Invention and evolution are engineering. Erik Naggum
The world belongs to the enthusiast who keeps cool. William McFee