Doubt is part of our humanity. As finite beings we should doubt. 1. We are limited in knowledge... so there are many things that we don't know. 2. We are limited in reason... so we cannot be fully...
Both are correct, and other possibilities exist. This is because "no doubt" is what we call absolute: it has no grammatical connection to the rest of the sentence. There might be variations in...
As far as I know its about Hamlets love for Ophelia (or alleged love). It means you can doubt the stars are made of fire, doubt the sun does move (like they believed that the Sun revolved around the...