In plain words
It is for such Ānanda that the Veda keeps warning man in so many ways. God is Aprameya. He is caught by no pramāṇa. He is One whom no pramāṇa can recognise. To recognise such a God, we are searching for many pramāṇas. God is beyond speech and beyond mind, and cannot be described: with what pramāṇas can we lay hold of Him?
Pramāṇas are of three kinds. One is pratyakṣa-pramāṇa. This is the very thing every man longs for today. He fancies, “For everything I must have direct experience.” He strives in many ways for pratyakṣa-pramāṇa alone. He cannot believe anything that has no pratyakṣa-pramāṇa. This is only the first step of Ajñāna. Pratyakṣa-pramāṇas come with diseases of many kinds. A small example. When our eye is healthy, black appears black, white white, red red, yellow yellow. This, precisely, is pratyakṣa-pramāṇa. “I have seen it; black is black and nothing else.” So you set out to argue; then in a while the disease called jaundice enters this eye, and everything looks only yellow; no other colour appears any more. How true is this pramāṇa? So the pramāṇas bound up with the senses are things that change. Many scientists look for such pratyakṣa-pramāṇa. For example, when you look at it at night, it is milk. When you put a little curd into the milk at night, by daybreak it turns to curd. The milk has become curd. This is pratyakṣa-pramāṇa. This is a physical, material pramāṇa. It does not apply in the least to the spiritual. For all the senses that experience this pratyakṣa-pramāṇa are themselves bound to change. With senses that change you cannot recognise the Satya that does not change. The second is anumāna-pramāṇa. When we look at a hill far away, smoke is rising there. Smoke is the reflection of fire. Seeing the smoke, we believe there is fire; but the fire is not seen by us. Is it fire, or is it steam! Yet the smoke alone is seen. But to fancy that there is fire, seeing the smoke without seeing the fire: that is anumāna-pramāṇa. An image appears to us, as of a man coming. From it we can say that some man or other is coming, but we cannot say that such-and-such a man is coming. So this pramāṇa of reflections is not one we can experience directly.