First of all, everything we know about how the universe works is based on an assumption: the very foundations of science are assumptions, and as a result science itself is really nothing more than a set of beliefs. The only thing you can know for a fact about yourself and the universe is that what is here and now is present as an experience, and even more, that experience is solely and exclusively not public. Even the idea of stepping outside that experience to make any observations about it’s origin and nature is incomprehensible.
Secondly, rebirth is not a life after death, it’s a completely new life of a new born being. What continues here is not a being, but a being’s assumptions about the continuity of itself, about own personality - ignorance. Rebirth is no different from waking up or even from any present moment of your life: on the same ground you assume the continuity of you right now or after waking up from the oblivion of the dream on the same ground there is the continuity of rebirth. Is the you reading this word now the same you reading the word you now? And how do you know this? What does this knowledge consist of? What are the facts and what are just assumptions and beliefs? And, most importantly, are you in control of that continuity, are you in control of that of which the experience you take as yours and of yourself is composed? Are you in control of the presence and continuity of you and what is yours?
The ultimate happiness is freedom. For without absolute mastery and control over that which is you and yours, unhappiness is still possible and would happen.
Noble means free. Ignoble means not free, shackled, subjected, fettered, not the master of one’s own happiness.