A very ancient rejection of substance and essence altogether, or their equivalents in Indian philosophy, began in Buddhism. Since the approach of Buddhism to the world is to break attachments, so that one does not suffer because of relationships to things, a simple way to do that is to say, in effect, that there are no things. If nothing is substantial or has any essence, this will do that job. What we get instead are the doctrines of "momentariness," "no self nature," and "relative existence." If everything exists only momentarily, then nothing is durable, and we lose that characteristic of substances. If there is no self nature, then there is nothing in things that makes them what they are, and we lose the existence of essences. If things only exist relative to other things, then (1) nothing exists independently and we lose that characteristic of substance, and (2) nothing has its own character, so we lose that characteristic of essence. So what is actually there? Well, what we see is the "form" of things, the external appearance. Since there is no self nature and things only have relative existence, what are things in themselves when we take away everything else? Well, Emptiness. This is not nothingness (a major heresy), but neither existence nor non-existence nor both nor neither. In other words, we can't say or comprehend what is there. Later, in Mahâyâna Budddhism, we get the doctrine of the Heart Sutra that "Emptiness is Form, and Form is Emptiness."
