To investigate means to rectify — to correct what is incorrect and return to correctness.
"To correct what is incorrect means to remove evil. To return to correctness means to do good."
先生曰：「格者，正也。正其不正以归于正之谓也。正其不正者，去恶之谓也。归于正者，为善之谓也。夫是之谓格。《大学》之『格物致知』者，致吾心之良知于事事物物也。致吾心之良知于事事物物，则事事物物皆得其理矣。事事物物皆得其理者，格物也。是合心与理而为一者也。」
The Master said: "To investigate (ge) means to rectify (zheng). It means correcting what is incorrect to return to correctness. Correcting what is incorrect is called removing evil. Returning to correctness is called doing good. This is what is meant by investigation. What the Great Learning calls 'investigating things and extending knowledge' means extending the innate knowledge of my mind to all things. When I extend the innate knowledge of my mind to all things, then all things attain their principle. All things attaining their principle is investigating things. This is uniting mind and principle as one."
Yangming's investigation is the daily practice of "removing evil and doing good" — not a distant philosophical concept but a moment-to-moment practice. For every thought, ask yourself: is this the voice of innate knowledge, or the drive of selfish desires? Correcting incorrect thoughts is investigation of things.
"To investigate (ge) means to rectify (zheng)."
This is Yangming's final definition of "investigation of things." Ge is not Zhu Xi's "to reach" (arriving at things), but "to rectify" — correcting what is incorrect. Investigation is not about exhaustively studying external principles, but about correcting the inner mind's incorrectness. This definition unifies investigation with rectifying the mind.
"Correcting what is incorrect is called removing evil."
The two aspects of investigation: removing evil (correcting the incorrect) and doing good (returning to correctness). This is not passive prohibition but active return — returning to the mind's innate goodness. Removing evil is not destroying something but removing obscuration; doing good is not adding something but restoring the original state.