"Thus it is clear that man does not possess any criterion of knowledge that can be relied upon."

... "Know, therefore, that what the people possess and believe to be true is liable to error. For if in proving or disproving a thing a proof drawn from the evidence of the senses is advanced, this criterion is clearly imperfect; if a rational proof is adduced, the same holds true; and likewise if a traditional proof is given. Thus it is clear that man does not possess any criterion of knowledge that can be relied upon.

But the grace of the Holy Spirit is the true criterion regarding which there is no doubt or uncertainty. That grace consists in the confirmations of the Holy Spirit which are vouchsafed to man and through which certitude is attained."

‘Abdu’l-Bahá, Some Answered Questions

Mishkin Qalam