本文認為朱子的理氣論固然具較強的思辨性，但其思辨是為了道德實踐的要求而作，並非為了滿足理論要求。由此，文中分析退溪（滉，1501－1570）、奇蘆沙（正鎮，1798－1879）等二位在韓國儒學史上被稱為主理派的代表人物對朱子理氣論的看法，來解決一般認為朱子「心是氣，理不活動，實踐動力不足」的理論困難。李退溪的「理發說」，應引入朱子弟子陳淳（字北溪）「心是理氣之合」的講法，不必說成理本身直接表現為活動，而是表示理在心中可以直接起用，心可表現出純理的行為，不受氣之影響。本文又分析了奇蘆沙的「主理」論證，認為蘆沙所強調的理的主宰性很可以用來解釋朱子之說。蘆沙認為，氣的活動是受理所主宰決定的，理雖然無形無狀，並沒有具體的活動作用，但無形的理對有形的氣具有最大的主宰力量，用此意可以說明道德之理本身雖無形氣作用，但具有特殊的力量，是可提供實踐動力的。通過二氏的見解，便可在不違背朱子理不活動的規定下，進一步闡明朱子理氣論中本具實踐動力之義。

In this article, I intend to show that even if Zhu Xi's li-ch'i theory has obvious speculative characteristic, the main reason of it is because of the requirement of moral practice, but not to satisfy the requirement of the theory. Commonly, people think Zhu Xi's main perspectives that hsing is ch'i and li has no motive power cause the dilemma in his theory, and they also think that the main problem of it is that the theory lacks practical incentive. To resolve the above problem, this article plans to discuss two Chosan philosophers, Lee T'oegye (1501-1570) and Chi Lu-Sha (1798-1879), who were regarded as the representatives of rationalistic school in Chosan dynasty. As for Toegye, his main perspective is li-fa theory. I intend to combine his theory with Chen ch'un (Zhu Xi's disciple), whose thought that hsin combines li with ch'i to point out the idea that hsin which li roots in can embody li directly without the influence of ch'i. As for Chi Lu-Sha, he claimed that li has particular power to control ch'i, so ch'i is under the domination of li. According to Lu-Sha' saying, there is no question that li can provide people practical incentive. Through the above Chosan philosophers' perspectives, this article concludes that even if Zhu Xi's li-chi theory has practical incentive, it still won't disobey his perspective that li has no motive power.