Hmmm well there are things I agree with and disagree on the first two reply's to my topic. As far as I have witnessed 3 dimensional life forms do not possess the ability to physically move through the forth dimension. The idea that a dream or memories is a subconscious way of slipping through the fourth dimension is a hypothesis that I think has some probable ground but not enough factual evidence to constitute it as a scientific theory. I do enjoy the idea though, and as bending the 2nd dimension through the third dimension objects in the 2nd dimension can basically telleport from spot to spot, ideally the same is possible from the forth dimension to the third. But this is only speculation.
As for us moving in the third dimension, I think we have that pretty much down. Now we are not able to fly no, and yes birds have more freedom in three dimensions without the aid of technology, but we still move in all three dimensions. Width, Height, and Depth. Even if we didn't move at all, lets say if we were a rock, we would still exist fully in the third dimension. Birds simply aren't as confined by gravity as humans, in space (and the lack of gravity) we would have the same amount of freedom of movement.
Life: an organismic state characterized by capacity for metabolism, growth, reaction to stimuli, and reproduction.
*chuckles* but in all seriousness I get what you are saying "Defiance". It is silly to think that we are the only creatures living in the universe. I think it's silly to think anything in absolute, personally, though I accept many concepts on majority acceptance and repeatability. I think that basing our search for life on what we experience here on earth is a decent strategy though. We understand how life works here to a degree, how it survives, reproduces, and evolves. From deep underwater volcanoes that support life in even the harshest of circumstances, to insects that have to live within only a small varying degree of temperature. This is not to say we shouldn't think outside the box, but life here on earth gives us a good foundation to base in the searching and defining of new life discoveries.