I believe there are other intelligent life forms out there simply because the universe is so vast and there are so many other galaxies and planets, so that if we exist there’s a pretty good chance others exist as well.
This argument is very common, yet for the life of me, it has never been convincing at all. For several reasons.
No matter how many monkeys are at a keyboard, none of them will ever randomly write a coherent book. The argument for vastness is dependent on statistics, but that has to assume a random distribution of possible outcomes. Even disregarding any theological thought, do we know this is what we are dealing with.
From a theological point if view, there is no reason why God could have or could not have created life elsewhere. The size of the universe is insignificant to God. Saying that He would have not created a large universe for just us begs the question: is our understanding of God that limited?
Also, from a theological standpoint, God the Son has two nature’s, only two. Now other intelligent life might not have sinned, but that just brings us back to the large universe problem and we would say, why just us? Others might have sinned and be saved by another means, but we are back to the large universe problem of why we are so special.
Genesis certainly implies mankind is the epitome of God’s material creation.
I could go on. I am not saying there are no other rational beings out there, but we have zero evidence of it. So we create a statistical argument that is weak. And if we are Catholic, we ignore revealed evidence that suggests otherwise.