Bare with me, Im young Please Register or Log in to view the hidden image! Why are viruses not considered alive? The typical answer I get to that question is that they cant survive on their own and are too dependent upon host cells, so they cant be alive. But how does that differ them from parasites? Tape worms cant survive unless they have a host organism, we consider them alive. In fact, there aren't many organisms, if any, that CAN survive without depending upon other organisms. So why do we single out viruses? I've also read that they aren't alive because they cant respond to stimulus. If it cant respond to stimulus, then how does it know to reproduce when it finds a cell? If it has a different reaction when it is next to a cell that it can use to reproduce than when its alone and as no opportunities to do so, isn't that a reaction?