I do not disagree with this, nor (I suspect) would most philosophers. The story of The Matrix is possible .But as long as we're talking about possibility, your situation might beeven worse than the one depicted in the movie. At least in the filmwe're all sharing the same, collective hallucination, but it might bethe case that you're the only one plugged into the Matrix.Perhaps you don't even have a full body; you might be just a brainfloating in a vat of nutrients and connected to a computer that isfeeding it electrochemical signals. In the Meditations ,Descartes famously considers an even more radical possibility: theentire material world could be an illusion. You could be a disembodiedghost dreaming that you have a body or a disembodied mind beingdeceived by a malicious and powerful demon into believing that there isa material world. Philosophers usually discuss outlandish thoughtexperiments such as these in order to raise questions about thepossibility of knowledge. Does knowledge...

Does something need to have "application" in order to be of value? Idon't know what sort of application the symphonies of Beethoven or theplays of Shakespeare have, but these works of art are of greataesthetic value. Space exploration is (at least in part) about thepursuit of knowledge. We explore space in order to come to a betterunderstanding of our home--the universe of which we are, it seems, avery small part. That seems worthwhile to me. (And of course it's worthbearing in mind that many inventions of great practical applicationhave come about as the result of experiments conducted merely in theinterest of scientific discovery.) That said, your point iswell taken; there are certainly more pressing needs at the moment. Andthe (roughly) one trillion dollars it would cost to put together amanned mission to Mars could be used to feed and take care of a greatmany people in need. Who knows how many diseases we could cure orfamines we could avoid with that sort of money? To answer yourquestion, then,...