Justifying the Four Noble Truths without rebirth In the article entitled A Secular Evaluation of Rebirth, Doug Smith, of the Secular Buddhist Association, wrote:


  It is for reasons such as these that any contemporary, scientifically
  informed Buddhist practice should reject belief in rebirth and its
  associated kammic causation. The Path is rich enough without them.


It appears that many Secular Buddhists do not accept rebirth, while almost all other Buddhists do.

In the essay entitled Dhamma Without Rebirth?, well-known Tripitaka translator and scholar Ven. Bodhi conveyed the mainstream view of the Buddhist world:


  If we suspend our own predilections for the moment and instead go
  directly to our sources, we come upon the indisputable fact that the
  Buddha himself taught rebirth and taught it as a basic tenet of his
  teaching. Viewed in their totality, the Buddha's discourses show us
  that far from being a mere concession to the outlook prevalent in his
  time or an Asiatic cultural contrivance, the doctrine of rebirth has
  tremendous implications for the entire course of Dhamma practice,
  affecting both the aim with which the practice is taken up and the
  motivation with which it is followed through to completion.


If someone considers himself a Buddhist, we can assume that he accepts the Four Noble Truths and the Noble Eightfold Path. I guess this should apply to Secular Buddhists as well.

If there is no such thing as rebirth (or continuation of the stream of consciousness or mind after death, in a new life), then there is no need to end suffering by ending craving (third noble truth), through following the Noble Eightfold Path (fourth noble truth). Instead, it's much easier to commit suicide, or simply wait for natural death. After all, if there is no rebirth, then at death, all suffering would end anyway, right?

So, based on this, how do Secular Buddhists justify their acceptance of the Four Noble Truths and the Buddha's teachings in general, if they reject rebirth? How would the Four Noble Truths and Nibbana have any meaning or usefulness for them? Why would they choose to follow the Noble Eightfold Path, if death is a much simpler way to end suffering?
Anti-rebirthist = ucchedadiṭṭhi =  one extreme.
Rebirth-lover = sassatadiṭṭhi = another extreme.
Profit-follower = eightfold path  = middle way.


1st and 2nd see brahmajālasutta.

3rd see dhammacakkappavaḍḍhanasutta. (I am in plan to re-translate this sutta, but I can't not done it now. So if something wrong, I am sorry. I can't not check it deeply now, because my english still not good enough.)


  "There are these two extremes that are not to be indulged in by one
  who has gone forth. Which two? That which is devoted to sensual
  pleasure with reference to sensual objects: base, vulgar, common,
  ignoble, unprofitable; and that which is devoted to self-affliction:
  painful, ignoble, unprofitable. Avoiding both of these extremes, the
  middle way realized by the Tathagata — producing vision, producing
  knowledge — leads to calm, to direct knowledge, to self-awakening, to
  Unbinding.
  
  "And what is the middle way realized by the Tathagata that — producing
  vision, producing knowledge — leads to calm, to direct knowledge, to
  self-awakening, to Unbinding? Precisely this Noble Eightfold Path:
  right view, right contemplate, right speech, right action, right
  livelihood, right effort, right mindfulness, right concentration. This
  is the middle way realized by the Tathagata that — producing vision,
  producing knowledge — leads to calm, to direct knowledge, to
  self-awakening, to Unbinding.


What is profit?

6 profit: self profit, the others' profit, public's profit (common interest), this life's profit, next life's profit, and nibbāna-profit. (pali for search: attattha, parattha, attaparattha, ditthadhammika, samparāyika, and paramattha.)

Self profit, the others' profit, and public's profit (common interest) are done together by sati.


  "Because of what I have said here, monks, you should train yourselves
  such that the gifts of those whose requisites we use — the robes,
  alms-bowl, chair, bed, and medicine as a support when sick — will have
  great fruits, great merits [for the people who give them], and our
  going forth will not be in vain, will be fruitful, will have a result.
  Thus should you train yourselves, thoroughly seeing that for your own
  benefit, monks, it is right to strive with heedfulness; thoroughly
  seeing that for the benefit of others, monks, it is right to strive
  with heedfulness; and thoroughly seeing that for the benefit of both,
  monks, it is right to strive with heedfulness."


This life's profit and next life's profit are done together by sati (appamāda). So, person who do just this life's profit or next life profit is pamāda person. see:

http://www.accesstoinsight.org/tipitaka/sn/sn03/sn03.017.than.html

Nibbāna profit can be accessed by practitioner after he perfect finished to meditate magga.  And that magga can start to meditate after sīla is done. 


  SN 45.149 Just as, bhikkhus, whatever actions are to be performed with
  strength are all performed on dependence on the earth, supported by
  the earth; in the same way, bhikkhus, it is on dependence on virtue,
  supported by virtue, that a bhikkhu develops the noble eightfold path (magga),
  that he cultivates the noble eightfold path.


Above sīla give this life's profit and next life. See (1st-4th are this life's profit, 5th is next life's profit):


  Mahāparinibbānasutta
  24. "Five blessings, householders, accrue to the righteous man through 
  his practice of virtue: great increase of wealth through his
  diligence; a favorable reputation; a confident deportment, without
  timidity, in every society, be it that of nobles, brahmans,
  householders, or ascetics; a serene death; and, at the breaking up of
  the body after death, rebirth in a happy state, in a heavenly world."


So, anti-rebirthist &amp; rebirth-lover are pamādo (person who has not meditating mindfulness).

That is one of many reasons that why I, who have never seen any ghost or any spirit, am not deny next life.