4.40 Ajnah, one who is ignorant, who has not known the Self; and asradda-dhanah, who is faithless; [Ast. adds here: guruvakya-sastresu avisvasavan, who has no faith in the instructions of the teacher and the scriptures.-Tr.] and samsaya-atma, who has a doubting mind; vinasyati, perishes. Although the ignorant and the faithless get ruined, yet it is not to the extent that a man with a doubting mind does. As for one with a doubting mind, he is the most vicious of them all. How? Na ayam lokah, neither this world which is familiar; na, nor also; parah, the next world; na sukham, nor happiness; asti, exist; samsaya-atmanah, for one who has a doubting mind. For doubt is possible even with regard to them! Therefore one should not entertain doubt.
Why?