所有的曾经被发现的事实/曾经做过的实验/曾经做的任何事，只要不被认为是常理的 都用过去式。只要被认为是常理的，都用现在时态。 This may possibly suggest that you must read one particular sentence or paragraph much more than once. You may also desire to reread The full piece. That is great.[1]