There’s nothing religious, spiritual (from the Latin: spiritus, meaning breath, hence breath-full) or psychic (from the Greek: psyche, according to St Paul meaning soul, hence soulful) about the heart (or core) of Buddhist belief. It simply states:
“All that is subject to arising is subject to cessation.” (to wit: nothing lasts).
“A thing arises because of conditions; it ceases when the conditions for its arising cease!” (to wit: all things are as empty boxes, that is to say, empty of abiding substance or essence).
“If you attach to (or desire) something that doesn’t last because it has no abiding substance/essence you’re going to get hurt. Ergo, Detatch! ”
In short, all things (i.e. appearances) are empty (i.e. of abiding substance or essence), albeit colourful (hence attractive) boxes (i.e. transient effects, hence affects clusters).
The heart (or core) of Buddhist belief is secular, profane (from the Latin: profanus, meaning outside the temple). No God, gods, saints or priests are required to reduce and eliminate one’s attachment to that which doesn’t last and, consequently, one can’t own.
So where did the Buddhist religion, complete with populist belief in gods, devils, karma, transmigration, faith in the Buddha, subservience to priests and so on come from?
It can be assumed that Gautama, who had declared himself fully awakened (though he offered no proof), was a highly intelligent and persuasive individual, hence charismatic, therefore powerfully attractive. In other words, he was regarded (indeed experienced and treated) as a star (performer, like a film star or a billionaire industrialist or Indian godman), hence ‘heavenly’.
It’s human weakness/need to worship (or adore, therefore attach to) stars (the heavenly).
With his death, the Buddha’s capacity to attract and retain paying customers also died (the same problem arises in India when a famous, and usually obscenely rich godman/guru (like the recently ‘ceased’ (empty but colourful box) Sai Baba) dies). So his corrupt priest resorted to a bit of reverse engineering.
Since the actual star (or god-like) performer had ‘ceased’, and with his death the income flow and access to power and influence, his priests simply kept him quasi alive in relic collections and ‘present’ holy caves or temple rooms. They then elevated him to god (i.e. high attraction) status and created a welter of fantastic stories that placed him in the company of gods, and whom he regularly outsmarted. In this way those corrupt (indeed, very worldly) priests played to the populist need ‘to worship and adore’ (and be comforted by godly presence) and so kept themselves in (a lucrative) business.
In essence, the core Buddhist cure-all stated that ‘Nothing lasts, therefore don’t get attached’. Once the initial impact of this striking new message had dissipated and people wanted – indeed needed – more, the Buddha’s successors created (over the next 1500 years) a vast array of colourful packaging for the essentially boring core message about transience and emptiness. That was a smart move in that the common folk, smart (i.e. awakened) by nature, always succumbs to the greater delight of buying into packaging (or cosmetics) rather than content (i.e. ordinary everyday fact). And that’s actually very smart since there is no content to any package, or so the Buddha had claimed. ‘All we get (and therefore are) is temporary packaging’, so Gautama, and which is really only half the story.