Having exhausted the ascetic practices, the Buddha sits down beneath the Bodhi tree and resolves not to get up until he has solved the problem of conditioning.

Overview: The Buddha's Awakening

In discovering the middle way, the Buddha realized that karmic conditioning is not a purely physical problem that can be resolved through physical practices. In fact, Siddhartha discovers that the problem of karmic conditioning is really much more about the mind. This leads him to the path of cultivating wisdom. 

One way of thinking about this is that mental conditioning—karma—is what drives us to act in the world. It causes us to seek things we believe will make us happy and avoid things that we find unpleasant or dangerous. In other words, how we interpret our experience drives our attempts to get what we want and avoid what we don't want. "If I could just have this, I'd be perfectly happy." "If I could just avoid this person, and never see them again I'd be happy—or at least less unhappy!" But, as it turns out, these interpretations are wrong.

A mistaken need for ice cream

The idea—widespread in Siddhartha's time—is that objects are not able to make us happy, no matter how much we get or avoid, because we have a true, inner soul that is not of the nature to be satisfied by ice cream, for example. This soul, this atman, is transcendent—made from different stuff. This means that the urge to get ice cream is a confusion about what we really need. 

So Siddhartha begins pursuing the path of wisdom. He becomes interested in the true nature of this self that he is trying to make happy and to free from dissatisfaction. In doing so, he discovers something very different to what the spiritual thinkers of his time are proposing.

No self, no problem

Siddhartha does not find a spiritual essence that cannot be satisfied by material pleasures. Rather, as he meditates beneath the Bodhi tree, Siddhartha finds that the fundamental problem is this very idea of a spiritual essence, a core identity, an unchanging "me" that we need to make happy and protect from suffering. There isn't any transcendental, irreducible self... but we are also not nothing at all. Our true nature is between these extremes. It is this discovery that liberates Siddhartha from suffering and he becomes the Buddha: one who has awakened from confusion, one who has blossomed into full realization.