首楞嚴義疏注經 10.95

10.95

念念生處，名各各有，因是得證一切皆有。有人來問但答是者，雖見其心念念有生，意計皆有，又見其滅，不敢答有，故但答是，擬防其失。

Where there is arising from moment to moment is called 'each exists'; through this he attains realization that everything exists. When someone comes to ask, he only answers 'yes': although he sees his mind arising from moment to moment and internally calculates that all exist, seeing its cessation as well, he does not dare answer 'it exists', so he merely answers 'yes' in an attempt to guard against error.