thinker

One who devotes much time to thought or meditation.

One who thinks or reasons in a certain way.

One who thinks; especially, one who has cultivated or exercised to an unusual extent the powers of thought.

One who thinks; especially and chiefly, one who thinks in a particular manner

One who spends time thinking, contemplating or meditating

An intellectual, such as a philosopher or theologian

an important intellectual

someone who exercises the mind (usually in an effort to reach a decision)