The answer to this question for me at least is incredibly obvious, especially in light of all the recent astronomical observations of planets around other stars and considering the huge estimated numbers of planets similar to earth in the universe. It's a matter of probability! Thus far of course, scientists have no direct proof of life outside the Earth, but what do people think? Y or N?
The Fermi Paradox suggests there is a high probability of extraterrestrial life. So, I think keeping an open mind about the existence of ETs rather than denying the possibility is the better way to think. When proof presents itself maybe I'll feel a little better inside.
For me it's not really a paradox that there are high estimates for the probability of alien life and yet a lack of evidence, as there are such vast distances between solar systems. This may prove or not prove to be an impenetrable 'barrier' to meeting other life forms directly. However, I am hopeful that with improving radio telescopes and other receiving instruments that in the future we would at least be able to pick up signals proving their existence, signals that could only have come from another intelligence.