「自然」是中國思想的重要概念，理學家雖不特別著重此義，但其核心概念卻不離此義。除了日常用語下的「自然而然」之意以外，理學家所用的「自然」大抵有二：（一）「自然」作爲天道創生行爲的述詞，或者「道」之屬性所具備的的自存性質。（二）在工夫論上，表示一種和「作爲」相對立的語彙，它表至高境界的狀態詞。依理學家的「自然」義，理學思想不能以當代的主觀唯心主義視之，也不完全是主體主義，因爲所有成熟的道德行爲都要依理行事，「自然」要建立在「必然」之基礎上。

"Nature" is one important notion of Chinese philosophy. Though the Neo-Confucians did not specifically emphasize its significance, their key concepts nevertheless revolve about it. Besides the daily usage that means "spontaneously," the Neo-Confucians' notion of "nature" falls into two categories. The first one serves as the predicate for the Way of Heaven's doings of creation, or the self-existent state of the properties of Dao. The other is an opposite term to "unnatural" in the Doctrine of Efforts, an adverbial modifier for the ultimate state of Self-cultivation. According to the Neo-Confucians' concept of "nature," Neo-Confucian philosophy cannot be identified with the modern-day subjective Idealism, nor is it entirely Subjectivism. Because all mature moral conduct have to be executed in accordance with reason, "nature" has to be established on the basis of "necessity."