The ignorant, inattentive and doubtful indeed perish. For the doubtful, neither this world nor the other, nor again happiness is there.
Ignorance is the one culprit in human life in all fields of activity, performance and achievement. To be ignorant is the worst plight one can court. Likewise is inattention. For the attentive, knowledge will trickle from all quarters, events and persons. Observation itself is sufficient to learn the valuable lessons of life.
Doubtfulness is another traitor. If you start doubting everything, there is no end for the mischief. It makes oneself, the world around and his life of interaction, all false and useless. Such an attitude will make life utterly stale, directionless. The doubtful courts destruction.
For anyone like this, there is no meaning and purpose in this world. It holds no charm, interest or occupation. If this world is useless, so will be the others.
Even happiness and comfort one normally looks for will not be available for him. To doubt is to vitiate life completely. Safeguard against it. Live and seek to know.