content: 1  Wouldn't that just increase our exposure risk to other life forms?  2  This was essentially mentioned when discussing "type 3" civilizations. There could very well be some life form advanced enough to visit us, but they opt not to.  3  We do have attempted contact. Are you talking about alien contact with us? On the larger scale:  it makes assumptions  Everything in science makes assumptions. We assume our observations are accurate. We assume that, because something has happened n time, it will happen on the n+1 time. The difference is, these assumptions are made with less corroborating data. Until we are able to recreate all crucial steps to life, and determine likelihood of those events happening on goldilocks planets, we are just making vague guesses.