To what did the Buddha awaken?
When a Bodhisattva awakens they awaken to something. We might say a Bodhisattva like Siddhartha awakened to the absolute (dharma) thus attaining nirvana, or he realized the absolute and thus attained nirvana or beheld the absolute and thus attained nirvana. Of course, nirvana, itself, is a mystery for those not beholding and experiencing it directly. Nevertheless, it is something very transcendent and real. Here we read a description of it found in the Udana.
Monks, there exists that condition where is neither earth nor water nor fire nor air: wherein is neither the sphere of infinite space nor of infinite consciousness nor of nothingness nor of neither-consciousness-nor-unconsciousness; where there is neither this world nor a world beyond nor both together nor moon-and-sun. Thence, monks, I declare is no coming to birth; thither is no going (from life); therein is no duration; thence is not falling; there is no arising. It is not something fixed, it moves not on, it is not based on anything (anrmmanam = it cannot be made an object of thought or sense). That indeed is the end of Ill (dukkha).
Unfortunately, nirvana in the hands of pop Buddhists seems to be of little or no importance. According to Stephen Batchelor in his book, Buddhism Without Beliefs, this is what the Buddha awoke to.
The Buddha woke up to the nature of the human dilemma and a way to its resolution (p. 6).
And,
He awoke to a set of interrelated truths rooted in the immediacy of experience here and now (p. 6)
Sorry, but this is not what the Buddha awoke to, or saw, or came to know, or plunged into, or delighted in. By awakening to the absolute, a Bodhisattva like Gautama achieves nirvana and thus becomes the Buddha.
