Technically every hypothesis that fits our data should get a little weight, plus our best available models of the universe show there should be billions of planets as habitable as ours.

That is evidence in the abstract sense and we currently lack the technology to observe these candidate planets in enough detail to test the models further.

We're like a person sitting in the desert at night with nothing but a candle concluding that the planet is completely deserted because they can't see anyone else.

I don't think I've ever been in a desert where just by waiting a short time, visual evidence of an advanced civilization wasn't available (or in most cases, immediately).

If there's type II civilizations in our galaxy, we don't need to observe things in any more detail than we are now. If type III civilizations exist in other galaxies, we should be able to detect them as well.

There's also the Dark Forest Theory. Any civ advanced enough knows better than to broadcast information that could potentially help other advanced civs spot their location.

Yup, a number of possible solutions. Dark Forest doesn't lead to the likelyhood of us seeing UFOs in Ireland tho.

What about the Dyson dilemma? We've indeed detected "voids", but we're unable to confirm their origin.

If you have a dyson sphere, it glows very brightly in lower wavelengths, such as IR. We don't see that in voids. Additionally, looking back into cosmic history, we can see the formation of voids in the very early universe and their expected expansion.

I find the assumption that any advanced civilization is going to emit external electromagnetic radiation and/or be warm quite curious. Most quantum computing work is at low temperatures, and work on photonics (for example : http://science.sciencemag.org/content/361/6397/57 )is coming along nicely. If we assume an extropian approach of uploading into a more advanced substrate, I find it more likely that they would be quite cold in nature.

ok, fine, then they are blazing in the microwave region. The Dyson sphere will always output the same amount of energy as the original star, just at a lower frequency. Otherwise the temperature would increase continuously.

Pretty difficult to beat the laws of thermodynamics.

QC is a meme.

Honestly if you were put on a random desert on a random world you'd be more often right than not about how many people were on the rest of the world.

> Technically every hypothesis that fits our data should get a little weight

This sounds superficially right, but unfortunately there are too infinitely many possibilities to assign more than 0 weight to them just because they're compatible with the data. It's the same fallacy as "the sun either will rise tomorrow, or it won't. Two possibilities mean a 50-50 chance."

A more practical approach will only assign weight to possibilities that might influence your decisions about what to do.

The problem is that we have basically no data, in general people (including pilots) are horrible bad at observing and recounting a situation like these and we have no other types of evidence either...

One gloriously eldritch way to look at that issue is: can an ant see us? Are they aware of our existence?

Not really the same unless ants have mapped out their universe with little left out. Unless it's just that we can't see far enough or into dark matter.