But as with life on Mars, until you get a chance to take a look, how confident can you be one way or another?
If you don't look then you can't know for certain and therefore can't be confident at all. 
mnli hypothesis: If you don't look then you can't know for certain and therefore can't be confident at all.  premise: But as with life on Mars, until you get a chance to take a look, how confident can you be one way or another?