1. The eyes of doubt are like the eyes of an owl. They can only be seen in the dark, but light can make them lose their sight. ——Jokay Moore, "Black Diamond"

2. The key to all science is undoubtedly the question mark. ——Balzac's "Donkey Skin"

3. Doubt is the key to knowledge. ——Sadie's "Rose Garden"

4. Doubt is infinite exploration. ——Socrates, "The Sophists"

5. Faith and doubt complement each other. Without doubt, there is no true faith. ——Heise's "Song of Ticino"

6. The only limit to our understanding of tomorrow depends on our doubts today. ——Roosevelt, "Roosevelt's Narrative: Out of the Crisis"

7. Doubt is not the opposite of faith, but an element of faith. ——Romain Rolland, "Farewell to the Past"

8. If you want to be a true seeker of truth, there should be at least one period in your life when you should be as skeptical as possible about everything.

——Descartes "Principles of Philosophy"