本文旨在探討張載「大心」說之思想意涵。全文由下述三項提問展開：首先，通過追問何謂「大心」？本文將指出，張載一方面是由人能充分存養擴充自身本有的德性心，以達到體物不遺的境界，而言「大心」。另一方面，張載則是由超越成心私意的侷限，而言「大心」。其次，通過追問如何實踐「大其心」？本文將指出，張載是從「心御見聞」與「掃除成心」而言大其心的實踐工夫。最後，通過追問張載大心說與氣論的關連為何？本文將指出張載天道觀與心性論間的一貫之道。

Zhang Zai introduced the concept of mental expansion. The present study examines three questions regarding this seminal concept. First, what is mental expansion? According to Zhang Zai, one can reach a state of partaking of all the things only if one is capable of expanding and maintaining one's morals and conduct. Furthermore, mental expansion involves surpassing the limitations of selfishness and prejudice. Second, how can one expand the mind in practice? For Zhuang Zai, it is possible to expand one's mind through practical procedures; it is a matter of letting one's conscience control and guide one's faculties of reason and sensibility. Finally, what is the connection between the concept of mental expansion concept and Zhang Zai's fundamental notion of Qi? In conclusion, implications of this concept of mental expansion for Zhang Zai's notion of the Way of Heaven and theory of Mind-and-nature will be discussed in this article.