In a sentence: Life is bad, but so is death. Of course, life is not bad in every way. Neither is death bad in every way. However, both life and death… - David Benatar

Further insight into the poor quality of human life can be gained from considering various traits that are often thought to be components of a good life and by noting what limited quantities of these characterize even the best human lives. For example, knowledge and understanding are widely thought to be goods, and people are often in awe of how much knowledge and understanding (some) humans have. The sad truth, however, is that, on the spectrum from no knowledge and understanding to omniscience, even the cleverest, best-educated humans are much closer to the unfortunate end of the spectrum. There are billions more things we do not know or understand than we do know and understand. If knowledge really is a good thing and we have so little of it, our lives are not going very well in this regard. Similarly, we consider longevity to be a good thing (at least if the life is above a minimum quality threshold). Yet even the longest human lives are ultimately fleeting. If we think that longevity is a good thing, then a life of a thousand years (in full vigor) would be much better than a life of eighty or ninety years (especially when the last few decades are years of decline and decrepitude). Ninety years are much closer to one year than to a thousand years. It is even more distant from two thousand or three thousand or more. If, all things being equal, longer lives are better than shorter ones, human lives do not fare well at all.

Even the extent to which our desires and goals are fulfilled creates a misleadingly optimistic impression of how well our lives are going. This is because there is actually a form of self “censorship” in the formulation of our desires and goals. While many of them are never fulfilled, there are many more potential desires and goals that we do not even formulate because we know that they are unattainable. For example, we know that we cannot live for a few hundred years and that we cannot gain expertise in all the subjects in which we are interested. Thus, we set goals that are less unrealistic (even if many of them are nonetheless somewhat optimistic). Thus, one hopes to live a life that is, by human standards, a long life, and we hope to gain expertise in some, perhaps very focused, area. What this means is that, even if all our desires and goals were fulfilled, our lives are not going as well as they would be going if the formulation of our desires had not been artificially restricted.

A few of my critics have claimed that I am committed to the desirability of suicide and even speciecide. They clearly intend this as a reductio ad absurdum of my position. However, I considered the questions of suicide and speciecide in Better Never to Have Been and argued that these are not implications of my view.
First, it is possible to think that both coming into existence is a serious harm and that death is (usually) a serious harm. Indeed, some people might think that coming into existence is a serious harm in part because the harm of death is then inevitable.