What do you guys think of UFO's?

[Your Computer]

But that's the point. We are speaking for our current physics. Saying that our knowledge may be denied or that there is something we miss is in my opinion not logical. If is hypothetical. I am not speaking with hypothesis. You have to accept that our knowledge is correct even IF it MAY be proved that at some extent it isn't.

I explained that no planet in our solar system except earth is habitable. An alien can only come from outerspace.

I only have to assume it correct as far as it is practical. That is no different a position than what scientists are said to take. And it is logical to assume that it may be proved wrong. Are you going to deny me the aircraft i've seen? If every human is going to deny that they've built it, should i then go around believing that a human built it? Whatever was flying that aircraft is none of my concern. I only wish to know who (or what) built it.

And while you may have stated that the Earth is habitable, you also clearly emphasized (i.e. with underlined and bold words) that there is no possible way that an alien can live in this solar system, even though you knew better than that.