Idealist (noun)

1. A person who cherishes or pursues high or noble principles, purposes, goals, etc.
2. A person who is guided more by ideals than by practical considerations.
3. A person who advocates or practices a theory that the ultimate nature of reality is mental or spiritual.

Origin:

Mid 18th century: from french idéaliste, from idéal (see ideal).

Examples:

1. He was an idealist who believed in the perfectibility of humanity.
2. She was an idealist who wanted to change the world for the better.
3. The idealist's view of the world was often unrealistic.
4. The idealist's vision for the future was admirable, but difficult to achieve.
5. The idealist's philosophy was that the ultimate nature of reality is mental or spiritual.