Because the investigation of things and the extension of knowledge is a method of thinking, Ch'eng Tzu dealt with it first. In Erh Ch'eng i-shu [Legacy of the Two Ch'engs], section 25, it is said: "The Ta hsueh [Great Learning] states: A thing has its essentials and nonessentials, an affair has a beginning and an end. Knowledge of what is primary and what is secondary approximates the truth." Ch'eng Tzu maintained that the most important thing in study is to know (...) what is essential and what is nonessential - the beginning and the end. The extension of knowledge lies in the investigation of things; it is essential and constitutes the beginning. Governing the world and the state is nonessential and constitutes the end. Chu Tzu [Chu Hsi] said: "Ch'eng Tzu discussed the theory of the investigation of things in detail." But what is the extension of knowledge and the investigation of things? Chu Tzu maintained that "to investigate" [ko] means "to study thoroughly" [ch'iung]; the term "thing" [wu] means "principle" [li]. To investigate the thing is to study its principle thoroughly. A thorough study of principle leads to an extension of knowledge; without a thorough study there can be no extension. Consequently, he thought that the investigation of things is the beginning of truth and that the student who undertakes the investigation of things is already near the truth. Why? Because the student who undertakes the investigation of things can control his mind completely. Although the key to governing the state and pacifying the world lies in the person — as in the saying "governing the world and the state must begin with the person" — one who would govern the state and pacify the world must first cultivate himself. Cultivating the self is the key to governing the state and pacifying the world, and the means of cultivating the self are the investigation of things, the extension of knowledge, sincere thought, and a correct mind. Perhaps the reader will ask, what the relationship is between cultivating the self, on the one hand, and the investigation of things and the extension of knowledge, on the other hand? Cultivating the self belongs to the realm of ethics; investigating things and the extension of knowledge belong to the realm of knowledge. Given the fact that the cultivation of the self belongs to the realm of ethics and the investigation of things and the extension of knowledge belong to the realm of knowledge, how can an intrinsic relationship between these two dissimilar realms develop? We know that Ch'eng Tzu emphasized two kinds of knowledge, moral knowledge and empirical knowledge. He maintained that if there were only empirical knowledge, there would be only the physical person dependent upon external things without knowing truth. Moral knowledge is true knowledge; therefore, it is necessary to transform empirical knowledge into moral knowledge. Only when external, empirical knowledge and internal, moral knowledge are combined is there true knowledge. But how are empirical knowledge and moral knowledge combined? Chu Tzu elaborated on this point. In the collected writings of Chu Tzu there is an explanation of the couplet "Heaven gave birth to the people/There are things and there are laws" from the Shihching [Book of Poetry]: "Ta ya cheng min." Chu Tzu maintained that in the line "There are things and there are laws" from the Shih-ching, the word "thing" [wu] means "form" [hsing] and the word "laws" [tse] means principle [li]. "Form" is a metaphysical concept, and "law" is what is called metaphysics. Man certainly cannot be without this thing, but unless we understand the "principle" of this "thing," we have no way of knowing whether it conforms to the correct form of life or of deciding the appropriateness of the thing. We must, therefore, seek the principle of this thing. But even if we know the thing and seek its principle, we still have not reached "the limits of the thing"; "the principle of the thing" has not been thoroughly studied and our knowledge of it is not complete. Consequently, we must strive "to reach its limits." This is the meaning of the statement:Only by investigating the thing and arriving at the thing itself can the principle of the thing be known completely. When the principle of the thing is known completely, our knowledge of it is extended and focused. Without obscuration, weaknesses and insurmountable barriers, the intention cannot but be sincere and the mind cannot but be up-right. (shrink)