The Great Filter is a term coined by [[Robin Hanson]], postulating a stage in evolutionary development—somewhere between dead matter and *expanding, lasting life*—that is very difficult to pass through. The Great Filter would explain the seeming absence of alien technological civilizations in the observable universe. The Great Filter may lie in our future, or in our past. If it lies in our past, then we are very lucky, and have a positive future ahead of us. If it lies in our future, then we are almost certainly not going to survive the next era. If it does lie in our future, it must lie in our fairly near-term future, prior to our migrating to other planets, or sending self-replicating space probes. This may draw comparisons to [[Eschatology]].