Enemy of Progress
The human progress can be measured by many different things, but usually the first thing that comes to mind is science, and how it can profoundly improve our lives and our society. And what would be the biggest enemy of science? You might say it's ignorance, but it's actually time. Not time itself, but rather the lack of time, let me explain...
Science is an infinite subject, our universe is for the most part still a mystery, and there's only so much we can do with our small brains and the short amount of time we have on this earth. The human life expectancy today is around 73 years, and every time a person dies, all their knowledge is gone forever. Of course we can try to teach our children everything we know, but every generation at least piece of knowledge is lost. A lot of scientists, inventors and philosophers dies before they can finish their work, and the next generation, often don't even know where to start.
Death is the only certainty in our lives, for every tick on the clock we are a second closer to dying. Our machines are evolving rapidly, but we are stuck behind. You see, 10 thousand years ago we had sticks, now we have rockets, but we are still the same cavemen we were back then, and just as afraid of death as they were. All scientific progress is in vain if we don't solve the biggest problem of them all, which is our own mortality. Can imagine if we didn't have to worry about death, if we literally had all the time in the world? There's nothing we couldn't achieve.
You may think this would create some other problems, like overpopulation, because if nobody dies and people keep having children, the population will certainly go up very quickly. But contrary to what most people believe, our planet is far from being overcrowded, in fact most part of it is empty. Our planet's land area, excluding antarctica, is around 134.740.000 Km², and if we apply to this all area the same population density of the US state of California (97 people per Km²), the earth population could be 13 billion, and with the population density of Los Angeles (3.168 people per Km²) it could be even 426 billion. Besides, let's not forget that in the future we could create settlements in other planets, increasing even more the potential for population growth.
Either way, make no mistake, the biggest enemy of the human progress is mortality, and if someday our science find a way to outsmart death, that would be the beginning of an era that today we can only dream of.