Dependent Origination, 'here-&-now' & 11th & 12th link On this site there are some users who claim that birth &amp; death are mental phenomena, while other people argue that it's something physical.

Contextually, the Buddha lived in a time where other sects believed in some sort of an afterlife and/or 'soul transmigration', so perhaps Buddhism borrowed these principles as well, due to social &amp; cultural conditioning?

Today, 'Atheists' &amp; 'secular Buddhists' read the suttas with their modern 21st century understanding, which is not open for speculative, unverifiable things.They don't put the Buddha's context into account, where these things might have been quite important.

On the other hand, the Buddha invites us to see for ourselves &amp; to experience the teachings in the here-&amp;-now.

Since DO is about the origination of dukkha, how do we both see &amp; stop literal birth, death &amp; aging? Wouldn't this be completely in conflict with the here-&amp;-now principle mentioned above?

The aging &amp; death part in the sutta is straightforward. To quote:


  "Now what is aging and death? Whatever aging, decrepitude, brokenness, graying, wrinkling, decline of life-force, weakening of the faculties of the various beings in this or that group of beings, that is called aging. Whatever deceasing, passing away, breaking up, disappearance, dying, death, completion of time, break up of the aggregates, casting off of the body, interruption in the life faculty of the various beings in this or that group of beings, that is called death.


In the quote above I cannot see any 'self-views' are subject to aging &amp; death. Instead, I extrapolate from that quote that indeed something physical is happening (aging, decreptitude, casting off of the body, interruption in the life faculty).

So my question is: How do we really reconcile "Here-&amp;-now" teachings with speculative, unverifiable theories, such as repeated rebirths, agings &amp; deaths?
In the quote above I cannot see any 'self-views' are subject to aging
  &amp; death.


The quote about 'aging-&amp;-death' only includes one word in common with the definition of 'birth' ('jati'). This one common word is "beings" or "satta". A "satta" is literally defined in the suttas as a "self-view", as follows: 


  'A being,' lord. 'A being,' it's said. To what extent is one said to
  be 'a being'? Any desire, passion, delight or craving for form, Radha:
  when one is caught up there, tied up there (visatta), one is said to be 'a
  being.'... Any desire, passion, delight, or craving for feeling...
  perception... fabrications... consciousness... when one is caught up
  there, tied up there, one is said to be 'a being.' SN 23.2
  
  visatta: adjective: strongly attached; entangled.
  
  
  
  Why now do you assume 'a being'? Mara, have you grasped a view? This is a heap of sheer constructions: Here no being is found.
  
  Just as, with an assemblage of parts, The word 'chariot' is used, So, when the aggregates are present, There's the convention 'a being.'
  
  It's only suffering that comes to be, Suffering that stands and falls away. Nothing but suffering comes to be, Nothing but suffering
  ceases.
  
  SN 5.10


This answer to the question is not 'atheist' &amp; 'secular'. It is what the Buddha literally taught.