唯我論主張自我是唯一的存在，外在世界的事物和別人的心靈狀態都只是自我意識的內容，依附於自我的心靈而存在，其本身並不真正存在。唯我論是觀念論(idealism)的一種；就知識而言，唯我論認為知覺心靈的主觀歷程，「所知的」必然是「我」或「出自於我」的，即是說，除了我和我所形容的以外，更無所知。就形上學而言，唯我論認為除「我」之外，更無其他的存在。就主觀的觀念論而言，如柏克萊(G. Berkeley, 1685～1753)即認為除為自己所知覺的以外，無物存在。 唯我論的理論所持的理由是：任何有關事物存在與否的認知都基於個人的意識，個人不可能逾越經驗而主張「某些存在」或「不存在」，經驗的內容及存在僅有個人才能知覺，故經驗專屬於個人，當我們認為「存在」時，其實只是承認當前的經驗存在，即是承認自我的存在。 現代哲學中，唯我論者已有改變，如笛卡爾(R. Descartes, 1596～1650)之「我思故我在」仍然確定「我」為基本的存在，但對「我以外」的存在置於可疑的境地。到了洛克(John Locke, 1632～1704)，除了藉直覺知識賦予自我存在之外，又藉感覺承認外在世界的存在，已與柏克萊主張有異。康德(I. Kant, 1724～1804)在意識中區分「經驗我」和外在事物，但都在意識範圍之中。此後論者如布萊德利(F.H. Bradley, 1846～1924)從經驗的內容分析入手，認為經驗內容的組成是主客體交互作用的結果，因此外在世界物體的獨立存在並無疑義。唯我論的自相矛盾，在邏輯上從唯我的存在及其為人所了解的事實，已經預設有公共意義(public meaning)的存在，顯示「我」並不是唯一的存在者。
Husserl
especially dealt with this topic in the Fifth Cartesian Meditation which
expanded to become as long as the other Meditations put together. Here Husserl
radicalises the problem. The problem is not: how do I understand the other?
Rather Husserl's problem is: how is the other constituted for me? How does the
other enter into my consciousness? (4490/16797)
In the
end, Husserl will argue that seeing another person as a person is itself no
greater a mystery than any other form of constitution. Levinas will dissent
radically from Husserl on this very point. (4516/16797)
Though
Husserl was by instinct a 'methodological solipsist', someone who began his
enquiry as a 'solus ipse' (CM § 42), nevertheless, as we have repeatedly
stressed, he was always at pains to deny that his philosophy ended in
Berkeleyan idealism or a 'transcendental solipsism'. (4524/16797)
Husserl
acknowledges the intersubjective nature of our experience but always grounds it
on the subjective: "the world is continually there for us, but in the
first place it is there for me" (FTL § 96b, p. 242; Hua XVII
249).(4532/16797)
Moran,
Dermot. Introduction to Phenomenology . Taylor and Francis. 2000, Kindle
edition.
