Einstein said that his God is the God of Spinoza,. The latter said that
"existence" is god,. MMY uses the word "Being".
But Spinoza never quite got the connection between Quietism and the
Transcendent, although some of the methods he mentions in "Ethics" are similar
to Mindfulness techniques.
On the whole, George Fox's approach is more developed than that of Spinoza.,
the latter emphasizing a more mental approach, whereas Quietism allows the mind
to transcend itself.