在托克維爾政治思想中，民主一直是核心的議題，也引發大西洋兩岸知識界熱烈的爭論。直到今天，政治、學術、新聞等各界仍經常引用他的觀點。本文即就托克維爾有關民主體制的思想進行研究，並發現可分梳為民主社會一般傾向、民主社會潛在的腐化危機，及民主體制存續之道三個面向進行討論。而這三個相關的部分，更可就其內在邏輯整合而成共和主義研究途徑。 首先，在民主社會的特徵及其發展方面，托克維爾認為民主社會強調國民主權及身份平等，雖然使社會充滿活力；但也易於衝動，缺乏遠見，造成庸俗的中產階級政治。同時在資本主義及工業革命影響下，可能會形成個體主義，使得人際關係疏離，且對公共事務冷漠；也造成物質主義，只想追求物質享受。大多數勞工也會有異化現象，淪為工作的奴隸。不過，民主社會也會發展出諸如結社、地方自治等鍛鍊政治自由的機制，提供個體自主性及公民性格寬廣的公共領域。托克維爾並主張國家利用宗教、法律培養公民參與的熱情與美德。這種觀念下的國家對人生計劃並不中立，顯現共和主義多於自由主義的立場。 其次，在民主體制潛藏的腐化危機方面，托克維爾指出三種可能形式。一是因身份平等可能切斷封建社會原有的社會紐帶，使得個體孤立無援，必須服從統治的多數，終而導致一種多數專制─以一種社會一致性窒息個體的思想。二是因公民追求物質主義過甚，竟而完全退出公共領域，並召喚一種保護性權力，在民主自由的形式下，溫柔親切地奴役人民。此亦即民主專制。三是在民主革命初期或資本主義發達之後，必將出現中央集權。國家為解決工業社會複雜的問題，因應人民龐雜的需求，在多數授權下集中所有權力，破壞了政治自由得以維繫的各種機制。 第三，在民主體制的維繫方面，托克維爾的主張也充滿共和主義的色彩。例如，為使公民保持自由的技藝，他認為，公民應參與鄉鎮自治、結社（特別是政治結社）、陪審團。而在培養公共精神的美德方面，托克維爾強調宗教的重要性。藉由教條式信仰，宗教可培養公民認識「適當理解的自利原則」。而且，民主社會也有賴宗教提供一種道德與知識的權威。在這一方面，女性公民扮演了傳承與複製的重要角色，因而在托克維爾的民主思想中也占有一席之地。 本文最後提出國民主權、身份平等、公私領域、社會共識等四方面的引申討論，進一步分析托克維爾共和主義式的民主思想，對當前主流民主理論所能提供的貢獻。此外，也依個人見解評論其不足之處。 / Democracy has always been a core concept and a controversial issue in Tocqueville’s political thought at both sides of the Atlantic Ocean. Politicians, scholars as well as journalists still quote Tocqueville’s points at the present time. This thesis studies Tocqueville’s democratic thought, and analyzed it in three aspects: the general tendency of democratic societies, the potential danger of corruption in democratic societies, and the maintenance of democratic system. With the interlock between these aspects, this thesis integrated them into an approach of republicanism to Tocqueville’s democratic thought. For the first aspect, Tocqueville believed that with the emphasis on popular sovereignty and equality of condition, democratic societies will bring themselves diversified vitality. However, the societies will also be passionate and myopic, as the characteristics of mediocre bourgeois politics. Influenced by capitalism and industrial revolution, the prevailing individualism in democratic societies results in social alienation, public apathy and overwhelming materialism. Most workers will degrade into slaves of their works. On the other hand, democracy will promote associations, local self-governments which provide public spheres to practice autonomy and citizenship through the art of political freedom. Furthermore, Tocqueville requested the states to cultivate the passion and virtue of civic participation by means of religion and law. States under this requirement is not neutral toward citizens’ life plans, and seems more republican than liberal. For the second aspect, Tocqueville pointed out three possible forms of corruption from democratic societies: majority tyranny, democratic tyranny and centralization. First, majority tyranny results in extreme exploitation of equality of condition which cut off the original social bonds in feudal societies, hence isolate the individuals and render them totally helpless but to obey the ruling majority. Majority tyranny stifles citizen’s originality with social conformity. Secondly, mainly on account of materialism, citizens would escape into private life and material happiness, and moreover give away thoroughly public affairs to a tutelage power to enslave people gently within the liberal democratic form. That is democratic tyranny. Thirdly, centralization will present itself definitely, either during the early stage of democratic revolution or after capital economy is delivered. In order to solve the complicated problems in industrial societies, respond to a lot of diverse demands, the state concentrate all the power under the delegation of the majority, and destroy all kinds of mechanism which sustaining the art of political freedom. For the third aspect, Tocqueville offered republican solution to the maintenance of democratic system. He thought that citizens should take part in township self-governance, associations (especially political associations) and the jury. He also emphasized the importance of religion in teaching the virtue of public spirit, as well as cultivating the knowledge of “the principle self-interest properly understood” by dogmatic belief. In the same way, religion affords ethical and intellectual authority to democratic societies. In this regard, the female citizens play so important part of sustaining and reproducing these ethical and intellectual lessons that Tocqueville had to illuminate the role of women in his democratic thought. In addition to these interpretations, this thesis presents four related concepts for further discourse: popular sovereignty, equality of condition, public and private sphere and social consensus. Based on these discourses, the thesis evaluates the merit and deficiency of Tocqueville’s thought of republican democracy.