Source: pp 95 and 101, What Does It All Mean? A Very Short Introduction to Philosophy (1987) by Prof. Thomas Nagel.
This question assumes 2 below; if 2 is false, then I can understand that 1 is false.
Perhaps you have had the thought that nothing really matters, because in two hundred years we'll all be dead. This is a peculiar thought, because it's not clear [1.] why the fact that we'll be dead in two hundred years should imply that nothing we do now really matters. [End of 1]
The idea seems to be that we are in some kind of rat race, struggling to achieve our goals and make something of our lives, but that this makes sense only if those achievements will be permanent. But they won't be. [2.] Even if you produce a great work of literature which continues to be read thousands of years from now, eventually the solar system will cool or the universe will wind down or collapse, and all trace of your efforts will vanish. [🔚] In any case, we can't hope for even a fraction of this sort of immortality. If there's any point at all to what we do, we have to find it within our own lives.
[p 101:] Some people find this attitude perfectly satisfying. Others find it depressing, though unavoidable. Part of the problem is that some of us have an incurable tendency to take ourselves seriously. We want to matter to ourselves "from the outside." If our lives as a whole seem pointless, then a part of us is dissatisfied -- the part that is always looking over our shoulders at what we are doing. Many human efforts, particularly those in the service of serious ambitions rather than just comfort and survival, get some of their energy from a sense of importance -- a sense that what you are doing is not just important to you, but important in some larger sense: important, period. If we have to give this up, it may threaten to take the wind out of our sails. [3.] If life is not real, life is not earnest, and the grave is its goal, perhaps it's ridiculous to take ourselves so seriously. On the other hand, if we can't help taking ourselves so seriously, perhaps we just have to put up with being ridiculous. Life may be not only meaningless but absurd. [🔚]
If 2 is true, then how is 1 'not clear'?
Does the author change his opinion about 1, in 3? 1 appears contradicted by 3.