We re certainly alone on this planet, although some animals have varying degrees of consciousness.
If you mean are we alone in the universe... well, as a matter of plain statistics, I think it s likely there s intelligent life elsewhere in the universe, and probably in this galaxy.
The problem with statistics is that they re probabilistic, so the answer to your question is neither yes nor no, it s we don t know.
This is a perfect application for belief, actually. As it happens, I do believe that there are intelligent life forms elsewhere in the universe, and even in this galaxy. They haven t been here, of course -- chances are they don t know we re here any more than we know they re there.
Because it is a belief, of course, I do not assert that there in fact *are* ETIs because that would require being able to provide evidence that they do exist. Obviously, I don t have that proof, or I d be getting measured for my tux and learning a few words in Swedish for the Nobel ceremony later this year.