The Eternal Question is a term referring to the question "Are we alone in the universe?" posed by a member or members of an intelligent species. This question does not need to fit a uniform idea or quote, just as long as it conveys the same, or similar meaning. Other variations on the question can be "Is there a purpose to life?" or, "Is this all there is?" and so on. Whether or not these questions are what an individual considers to be the Eternal Question is all a matter of one's own perception.
Before an individual, or individuals answers the question, they often will create belief structures in order to answer this seemingly unanswerable question. Even if this question is answered, some still hold onto the beliefs created before the question was answered. If these beliefs are incorrect or correct with the answering of the question is all a matter of one's own perception.
Though some think the question is answered with the discovering of whatever the posed question is asking, many will often ask another "Eternal Question" and will continue to set the bar of answering higher and higher. So, in a sense, the question can never be truly answered. Or maybe it can, it's entirely dependent on what one thinks the question is, and how it is answered.