So there is birth and previous birth and its cause the desire or ‘Tanha’ as the Buddhists call it. Logically desire can only rise out of sense contact. Sense contact can only occur in an entity who could perceive Namarupa or names and forms.
Before we go further into the other causes it would be helpful to learn what this namarupa is. In Buddhism the definition of the term is a bit different from that of the Vedas. There Nama means name and rupa means form in their literal sense. They are determinate divisions of reality. Buddhists have a whole philosophy on names and forms!
To them ( if we could go by the commentaries) "Name" are the three groups beginning with sensation (i.e. sensation, perception and the predisposition) and "Form" is the four elements. You know what the four elements are-it’s the same air, water, earth, fire of the alchemists. The Indians used to include Akasha or space in the list of elements as well. But the Buddhists do not.
Name by itself can produce physical changes, such as eating, drinking, making movements or the like. (I find it a bit abstruse I must say! May be they included all the actions in name. This also is logical if we consider forms as objects alone). Anyway it is said that name alone is not sufficient to create the world. So form also cannot produce any of those changes by itself.
The interesting thing is that, both these are supposed to be produced by the conscious awareness of their existence (on the part of the ‘thinker’ obviously) and is fabricated just like that –out of the thin air just like! There is no material to make these from.
"but just as when a lute is played upon, there is no previous store of sound; and when the sound comes into existence it does not come from any such store; and when it ceases, it does not go to any of the cardinal or intermediate points of the compass;...in exactly the same way all the elements of being both those with form and those without, come into existence after having previously been non-existent and having come into existence pass away”