Answer: Presupposition
Explanation: In fact, this is under girds thinking because it is something that has been tacitly supposed, assumed, that is, it is meant as a starting argument from which to derive other arguments. It may also refer to the initial tacit community opinion from which a series of procedures will follow. This is, therefore, an assumption that may be at the level of a hypothesis, from which starts one when wants to prove something, or to challenge something, or an initial thought / belief, a premise that will follow some sequence of conclusions.
For example, one might say, "He challenged the assumption that there are other civilisations in space."
It can also go from what is known to assumptions, that is presupposition: "He is no longer a taxi driver." Presupposition would be: "He was a taxi driver."