首楞嚴義疏注經 10.44

10.44

生理即行陰，以見想盡，想能運動，今已息故，運動既無，不生滅理自然是行。此於生滅計不生滅，故執為常。

"The living principle" refers to the aggregate of volitional formations. Because he sees that conceptualization is exhausted, and conceptualization can cause movement, which has now ceased: since movement is absent, the principle of non-arising and non-ceasing naturally belongs to volitional formations. Here, within arising and ceasing, he calculates non-arising and non-ceasing; therefore he grasps it as permanent.