And that there is also and also other planets, where the human race can give birth again, each time {i.e. life} on the ladder of perfection. That is the idea that Thomas creates for eternal return. We are also the inhabitants of this Earth {i.e. the number one planet, the planet of lack of experience}, of course, we can only form a very vague idea of what will happen in the case of man in other planets. Will it be more heavy? Will perfection be within his reach? Will he be able to reach it by repetition? Within the horizon of this yellowia alone, the concepts of pessimism and optimism can have a meaning: the optimistic is the one that imagines that human history will be less permanent on Planet No. 5. The pessimism is the one that does not believe this.
The quote suggests that humans have the potential for rebirth on other planets, representing a chance to progress up a ladder towards perfection. The idea is linked to eternal return, where each life allows for further growth and experience. On Earth, however, we possess limited understanding of what existence might be like elsewhere, raising questions about whether other beings will face greater challenges or attain perfection more easily through repetition.
This concept introduces a dichotomy between optimism and pessimism regarding human history on different planets. Optimists believe that humanity's existence could be transient and less burdensome in places like Planet No. 5, while pessimists doubt this notion, indicating a spectrum of hope and despair in how we perceive the future of humanity across the universe.