It's a classic question which entails a variety of conspiracies, endless arguments, and pressure towards the government which must certainly be hiding something. However, I would like to answer this question through a purely philosophical lens using an approach which I've included on this site before.
The central doctrine which I live by is that what we cannot see does not exist, for we have no proof of its existence. I would like to apply this logic to the idea of extraterrestrials (assuming that there are no humans with knowledge of any life forms which the general population does not know about, since this seems to be a common fear among many skeptics) which, at this moment, have never been identified. We can dream all we want about the existence of aliens, but the fundamental problem is that we are in a state of uncertainty.
Inevitably, uncertainty means that we are in the gray area between a definite "yes" and a definite "no," and we clearly cannot take the former position since there would be no proof to support this perspective. However, there is truth in the latter position, even if it is the result of ignorance. We can comfortably say that aliens do not exist because we have never identified any sign of their existence, and consequently, until the moment that we see them, we cannot prove that they have a place in the universe.
This does not mean that we should stop developing tools in order to continue exploring the possibility of their existence. As humans, one of the most disturbing things to be confronted with is mystery because we lack any sort of grounding. Thus, scientific mysteries continue to be handed down from generation to generation so that we can eventually arrive at a solution. The alien dilemma is one of these examples, and it requires the consistent development of new investigations and materials. There is no reason to give up, but until we find something, we are forced to err on the side of negation.
This goes back to my central philosophy of the visible being equal to reality. The human brain is what constructs our realities, and without it, nothing would exist. It is an egocentric doctrine, no doubt, but the only one that we can adopt. Without humans to observe, write, and communicate the events which happen on earth, there would be nothing— a plain world with no proof of existence without a creature that is evolved enough to record and consider the greater significance of its environment. Our brain, consequently, is the reason behind everything, and we have no choice but to agree with this as humans. While there may be another species similar to us in another corner of the galaxy (and chances are that there might well be) that has constructed their own collective "World Spirit," (see post from Hannah Arendt's The Life of the Mind for more behind this idea) our lack of proof makes it so that we must accept our reality as the only one until we truly discover these extraterrestrial beings...
4/12/21