The Difference Between Logical Reasoning and Investigating Chan

Logical reasoning is inference; direct perception is straightforward and immediate—right here and now, with no need for further comparison or analysis. "Logic" (逻) and "reasoning" (推) both belong to comparison and analysis, and so does "辑" (ji): the original meaning of the character 辑 is to arrange boxes of varying sizes and lengths properly on a cart, which requires analyzing and comparing how well the boxes fit the cart body.

In investigating Chan (canchan), there is no language or words. When the questioning doubt is at its most intense, one encounters a condition, touches upon a state, and suddenly there is a corresponding sudden awakening—one slaps one's thigh: "That's it!"—and thus finds one's own birth mother. If one still uses logical reasoning and says: "Ten years ago my mother was forty; ten years later she should be fifty. This person's age is about the same as my mother's, so she must be my mother"—the result is that one recognizes a stepmother. At the time of death one regrets it, but by then it is far too late. Logical reasoning is all a mental activity of the mind consciousness; whoever the mind consciousness alone recognizes is a stepmother—only the one recognized by following the manas is the birth mother.

Whether or not the mind consciousness is in samādhi, it can engage in logical reasoning, and the result is understanding a principle. But attaining realization and seeing one's true mind both require possessing preparatory concentration (anāgamya-samādhi); only then can one investigate single-mindedly, and the result is sudden enlightenment. Logical reasoning, however, does not require much meditative concentration—a brief moment of mental focus suffices, and the degree of meditative power demanded is extremely low. Therefore the wisdom of logical reasoning is weak and feeble, incapable of attaining realization or seeing one's true mind. When meditative concentration is deep, the mental activity of the mind consciousness becomes restricted and cannot proceed normally; when the questioning doubt is extremely intense, the mind consciousness's mental activity also weakens. The better the meditative power, the weaker the mind consciousness's function, the stronger the manas's function, and the deeper and more subtle the wisdom of direct perception.