DJS there can be various sources of knowledge:
God, aliens, emotions, mind, instinct, others.
What some people do is seek to elevate the human mind as the only source of knoweldge to the exclusion of all others. I can see why that's psychologically appealing, because we all like the idea of certainty, especially JWs and former JWs, but (and here's the supreme irony) I don't think it's particularly rational or reasonable to say the human mind is the ultimate source of all truth. Either the human mind is the product of undirected evolution, in which case there is no reason to suppose it has a particular capacity for identifying truth. Or else the human mind is the result of divine direction, in which case it is the divine which is the source of truth which the human mind has been designed to be able to identify.