The meaning of "the moment a thought stirs, one has already deviated"

"Kuai" (deviation) means deviation, contradiction, or "not." When we stir up a thought, this mind that gives rise to thinking is no longer the original mind of the eighth consciousness. Because the eighth consciousness never gives rise to thoughts—especially thoughts within the worldly dharmas of the three realms, thoughts with language, words, sounds, and mental cogitations—the eighth consciousness never manifests such things. Only the deluded mind has thoughts. Because the manas' grasping at worldly dharmas never ceases and its preoccupation is unbroken, the mind consciousness must continuously give birth to all kinds of thoughts and ideas, arising and ceasing, intermittent and fragmented—impossible to grasp and tangled beyond unravelling. Therefore, for a person without the seed-wisdom of Consciousness-Only, all the thoughts that can be observed are concocted by the deluded mind; the mind that gives rise to thoughts is all deluded mind, not the original mind of the eighth consciousness.