It is unlikely that extraterrestrials have ever visited earth

What a pleasure it was to read. To meet the burden of proof, my opponent needs to show that:1. It is possible to assess the likelihood of extraterrestrials visiting the Earth.2. Such a visit is less rather than more likely. My opponent has indeed made statements about the likelihood of a visit. However, these statements are based on speculation rather than evidence. He cannot assess the likelihood of a extraterrestrial visit to Earth because of our complete absence of knowledge about extraterrestrials. In the absence of evidence, my opponent has made assumptions about extraterrestrial form, behavior capabilities and even motivation. These assumptions are heavily influenced by his knowledge of terrestrial life. However, the only thing we know about extraterrestrials is that they are not from Earth, by definition. We know nothing further. Specifically:assumption 1: we can guess at extraterrestrials' decision-making processesPro speculated: "The only reason anybody would come to earth is either if they already thought there was something very unique about earth of if they just happened upon earth while exploring the galaxy. "Even supposing that extraterrestrials have minds like ours (and why would they? ), it really is outrageous to assume knowledge of their motivationassumption 2: extraterrestrials would have visited Earth only while humans were aliveThe Earth is 4.5 billion years old [1]. Humans have been on it for, at most, 7 million years [2], only 0.16% of the time. Therefore, if an extraterrestrial visit occurred, it is much more likely to have been before humans evolved. assumption3: extraterrestrials are made of matterLife forms on Earth are composed of matter. They cannot travel at the speed of light. It would be rash to make assumptions about extraterrestrials based only on our observations of terrestrial life forms, however. Of course, I can't imagine a sentient life form that is not composed of matter. Happily, though, the possibilities of the universe are not constrained by my lack of imagination. assumptions 4 and 5: extraterrestrials live on planets and are roughly the same size scale as usMy opponent has assumed that extraterrestrials, like us, would have evolved bound to a planet and that they would be roughly the same size as terrestrial life forms. This would mean that, to get to Earth, they would need to "undertake a trip" and that the trip would involve complex technology. Given that we know absolutely nothing about extraterrestrials, these are extraordinary assumptions. I don't see why extraterrestrials need to be bound to planets like us, or why they might not be naturally nomadic, or even several light years wide. assumption 6: we would be able to perceive extraterrestrials, perhaps by SETIMy opponent claims that any intelligent extraterrestrials nearby "probably invented radio technology long before we did. " Why? Radio technology has been useful to humans because it supplements our natural limitations. I can't see how you can conclude that it would be useful or even interesting to extraterrestrials. conclusionI don't know if there are sentient extraterrestrials or not. I haven't the faintest idea, and nor does anyone else (ruling out conspiracy theories). Furthermore, should they exist, I can't speculate as to their form and qualities, let alone motivation. In such a knowledge vacuum, no conclusions can be drawn. We can't perceive any evidence of an extraterrestrial visit to Earth. That's as far as we can go. We don't know what evidence of such a visit would look like, or if there would even be any evidence. Therefore, any assessment of the likelihood of a visit is not evidence-based. Any opinions on the matter are interesting only in terms of what they say about the person making them. Like a Rorschach test.