If you don't doubt it, be 'bout it. Intuition is soul's watchman.

People who're nuts never doubt their own sanity. (The Killer's Cousin)

I'm like my mother, she thought, I search my joy for signs of sorrow ahead.

The question that is upon my lips (please forgive me) is the doubt in your heart

To try is to invite uncertainty. Where confidence goes, success usually follows.

When people feel doubt in their hearts, a certainty might be felt in an ice cream.

Scientific knowledge advances haltingly and is stimulated by contention and doubt.

You'll never be as good as the next page you write, or as bad as the last one.

Many people place facts above faith and that makes things seem impossible for them

If the opposite of certainty is doubt, humility must lie somewhere between the two,

If you fill your mind with wonderful thoughts, there can be no room left for doubt.

People, generally, are equally insecure. They just show it (or hide it) differently.

The road of doubt leads to the dead-end of despair. Time to change directions!" HS/el

In a middle of a war a single doubt about what you are fighting for could mean death.

More often than you might think, teaching science is inseparable from teaching doubt.