Is rebirth essential to Buddhist philosophy? Elements of Buddhism can be rationally accepted such as the suffering that arises through attachment, the benefits of meditation, and even the acceptance of anatta, or non-self. It seems, however, that a belief in rebirth cannot be accepted rationally. A believer must suspend rationality to accept a theory that describes the migration of some level of consciousness across a lifetime. A common analogy used is the light emitting from a candle. Nothing substantial transmigrates, however something passes over from one life to the next. This theory cannot be directly perceived. Therefore, it cannot be tested, or verified rationally. It is simply a metaphysical inference. 

Buddhism encourages debate and questioning of its theories, and to not accept everything on face value. How then can a Buddhist test this theory? Can one disregard this element of Buddhism? Is it an essential aspect of the philosophy?
From Ven. Bodhi's excellent short essay "Dhamma Without Rebirth?":


  The aim of the Buddhist path is liberation from suffering, and the Buddha makes it abundantly clear that the suffering from which liberation is needed is the suffering of bondage to samsara, the round of repeated birth and death. To be sure, the Dhamma does have an aspect which is directly visible and personally verifiable. By direct inspection of our own experience we can see that sorrow, tension, fear and grief always arise from our greed, aversion and ignorance, and thus can be eliminated with the removal of those defilements. The importance of this directly visible side of Dhamma practice cannot be underestimated, as it serves to confirm our confidence in the liberating efficacy of the Buddhist path. However, to downplay the doctrine of rebirth and explain the entire import of the Dhamma as the amelioration of mental suffering through enhanced self-awareness is to deprive the Dhamma of those wider perspectives from which it derives its full breadth and profundity. By doing so one seriously risks reducing it in the end to little more than a sophisticated ancient system of humanistic psychotherapy.