社會學家馬克斯．韋伯（Max Weber）將理性理論應用於西方音樂時，發現西方音樂具有系統性及結構性的理性特徵。然而，當音樂進入前衛藝術時期時，其聲響變得混亂、不可預測，其記譜則充滿高度詮釋自由。這是否暗示此時期的音樂失去韋伯所說的理性特徵？又或是，理性特徵已隨著音樂轉換？美國前衛作曲家約翰．凱吉（John Milton Cage Jr.）基於禪學重新定義音樂，發展出自創的繪圖作曲系統用以創作。從凱吉的繪圖作曲系統中可發現價值理性及目的理性的存在，因此本文將以凱吉的不確定音樂《鋼琴獨奏》為例套用理性理論，嘗試找出不確定性中的理性特徵。結果發現，《鋼琴獨奏》的系統性及結構性隱藏於碎片化的繪圖記譜中，故本文嘗試進行理性理論延伸，提出跨社會學理論的不確定音樂及繪圖記譜分析模式，以新視角剖析不確定音樂。

When the sociologist Max Weber proposed the theory of rationality and applied it to Western music, he found rational features in its systems and structures. Nevertheless, when music entered its avant-garde phase, its acoustics became chaotic and unpredictable, with its notations providing great freedom for interpretation. Does this mean that music lost its rational features, or that the rational features had transformed alongside these developments in music? The American avant-garde composer John Cage’s work may be an appropriate example to manifest rational features. Cage redefined music based on his interpretations of Zen Buddhism, and he then invented a graphic compositional system where we could discover value rationality and purposive rationality. For this reason, this paper attempts to apply the theory of rationality to Cage’s indeterminate music work Solo for Piano (1957-58), discovering rational features of indeterminacy; the result shows that rational features (systems and structures) are hidden behind fragmented graphic notations. Based on this, this paper attempts to propose a cross-sociological analytical model for indeterminate music and graphic notations and dissect indeterminate music from an original angle.