Do you think intelligent life exists?
We are not intelligent life yet, we are still animals until we achieve Type I status. That is, a civilization with complete control of death, sickness, weather, the ecosystem, and without destructive conflict (war) - essentially a species that has mastered 100% of earth's resources.
This is a Type I Civilization, a Type I is able to begin true space exploration - by this estimation they would eventually become a Type II and then a Type III.
Now because of the nature of a Type III, our telescopes would be aware of such a civilization if one existed because it would control an entire galaxy worth of resources and we can see many galaxies in our observable portion of the universe.
So then it has been questioned whether or not even a Type I civilization is possible beyond mere conjecture, as there are no signs of such in the cosmos...did every Type 0 civilization like ours destroy themselves with chemical, nuclear, biological, or electronic warfare? This is a very likely possibility.
Any arguments for or against the notion that humans can be nothing more than any of the primitive decaying biological species in the universe? Is intelligent life real?
There are some possible explanations as to why and how we cannot see a Type III even if one is out there. We can only see a small portion of the galaxies before we are looking around 13 billion year-old photographs of other galactic systems, therefore there is no way even planets could have been formed yet, much less intelligent life.
Another possible explanation, and one I favor, is the Transcendence Hypothesis. The Transcendence Hypothesis states that instead of expanding territory and continuing to consume greater amounts of resources, a Type I Civilization will instead opt to expand consciousness and further evolve intelligence past the mundane 3 dimensional parameters of space and time. They will have so much computing power in so little space that it will collapse space time, and they will emerge somewhere else - possibly a 4th dimension, giving them the ability to manipulate matter and energy through collapsing complex wave functions through their presence within a quantum superposition such as a 4th dimension type, should they manifest back in the 3 dimensional realm. Realistically they'd never come back to play God here, they'd more likely opt to continue their conscious evolution in higher planes of existence at an exponential rate, never to be seen or heard from again.