Everyone who observes himself doubting observes a truth, and about that which he observes he is certain; therefore he is certain about a truth. Everyone therefore who doubts whether truth exists has in himself a truth on which not to doubt.... Hence one who can doubt at all ought not to doubt the existence of truth.
I am, and have been for years, a confirmed anti-vaccinationist...I have not the least doubt in my mind that vaccination is a filthy process that is harmful in the end.
The majority of mankind is lazyminded, incurious, absorbed in vanities, and tepid in emotion, and is therefore incapable of either much doubt or much faith.
Doubt, indulged and cherished, is in danger of becoming denial; but if honest, and bent on thorough investigation, it may soon lead to full establishment of the truth.
There is nothing makes a man suspect much, more than to know little, and therefore men should remedy suspicion by procuring to know more, and not keep their suspicions in smother.
Given the millions of billions of Earth-like planets, life elsewhere in the Universe without a doubt, does exist. In the vastness of the Universe we are not alone.
The medical profession (is) a conspiracy to hide its own shortcomings. No doubt the same may be said of all professions. They are all conspiracies against the laity... (U)ntil there is a practicable alternative to blind trust in the doctor, the truth about the doctor is so terrible that we dare not face it.
There is no doubt that the actions of ISIS are designed to amplify their power and the threat that they pose. That helps them recruit. That adds in the twisted thoughts of some young person that they might want to have carry out an action that somehow they're part of a larger movement.