No. I accept the 99.9999999999% certainty that aliens exist. Belief is only required in the absence of evidence, and we have a shit ton of evidence for abiogenesis and unlimited planets and conditions. Aliens definitely exist out there.

I don't think they have come here though. As much as I wish they did.

I've read / watched a lot on aliens and there's a few cases I've looked into that really are unexplainable so, there's a chance..