What's a good philosophical theory?

Question:For having some mighty good practical applications...John Locke.

For keeping us grounded, away from mysticism...Spinoza

For having addressed some tough issues - Plato

For arresting originality compared to any other - Nietzsche

Best Answer - Chosen by Asker: For having some mighty good practical applications...John Locke.

For keeping us grounded, away from mysticism...Spinoza

For having addressed some tough issues - Plato

For arresting originality compared to any other - Nietzsche

nihilism

One that stands up to rigorous testing against reality.

right and wrong

Truth and reality don't need us.

Existentialism

knowing that nobody really cares.