I didn't originate the idea of a distinction between faith and belief. That goes back even past Tillich to much longer tradition of German theological scholarship (and perhaps in German those two words are not so synonymous as they are in English).

I'm a humanist. I don't believe in supernatural beings of any kind. The natural is all there is. If we discover anything new, it will also be part of the natural world.

Positing the supernatural is a way to try and safeguard cherished values from criticism. This is an important line of attack not just for atheists who want to criticize religion, but also for liberal religious people who want to criticize fundamentalists.

That's why the distinction between faith as EXISTENTIAL and belief as EMPIRICAL is so valuable. Without it we lose an important tool for showing the intellectual and moral bankruptcy of any arguments that attempt to ground moral values in supernatural phenomena.