We can't be afraid to examine/question our presuppositions. [=assumptions]我们绝不怕检验/质疑我们的假设。

The argument is based on the presupposition [=presumption] that there is life in outer space.论证基于太空中有生命存在的假设。

The argument is based on prejudice and presupposition.论证是建立在成见和假设基础上的。