How do we get knowledge-a priori or a posteriori?

Philosophers of the ancient times told that one can obtain knowledge through our intuition and self probing.Of course there may be one or two people in the world who might have found knowledge in this manner. But according to Valluvar knowledge is acquired as far as he learns as if water springs up as far as you delve deep in to the sand. Philosophical arguments are far from understanding by common people as we are.