Was it doubted that those who corrupt their own bodies conceal themselves? - Walt Whitman
To have doubted one's own first principles is the mark of a civilized man. - Oliver Wendell Holmes Jr.
My only regrets are the moments when i doubted myself and took the safe route. Life is too short to waste time being unhappy. - Dan Howell
I was either still dreaming or I had entered an alternate reality where I was a flippin' insane person. I doubted I had entered an alternate reality and a quick slap to my own face proved I wasn't still dreaming. -Sage Hannigan, Contingency - P.S. Martinez
An unpublished writer should doubt themselves. They should constantly wonder whether what they’re creating has merit. And then, having doubted, they should take up their pen and see if they can’t make it better. - Johnny Rich
It may well be doubted whether human ingenuity can construct an enigma... which human ingenuity may not, by proper application, resolve. - Edgar Allan Poe