There were things, vague and insubstantial, which he could not understand.
From it rose the towers and high-peaked roofs of the city, insubstantial as a dream.
So feeble and insubstantial did he feel himself that he repeated the word aloud.
The beyond is vague and insubstantial, but it is instinct with life and purpose.
Shuddering, insubstantial, but luminously apparent, ...