本文探討知覺哲學的核心問題：我們能否直接知覺到外在世界？此即著名的「知覺問題」（the problem of perception）。根據直接實在論（Direct Realism），知覺提供了對於外在世界直接的覺察（direct awareness）。但這樣的立場遭到「錯覺論證」（the Argument from Illusion）的嚴重威脅。在《知覺問題》（2000）一書中，A. D. Smith對於知覺現象（perceptual phenomenology）進行仔細的研究，而提出了一個新穎的理論來辯護直接實在論。按照Smith的理論，知覺的意向性（intentionality）是由三個特性來解釋，分別是：現象上的三度空間性（phenomenal three-dimensional spatiality）、運動（movement）、以及the Anstoss。Smith試圖論證：他這樣的解釋能夠抵禦錯覺論證最關鍵的前提，即所謂的「感覺與料推論」（the sense-datum inference）。 在陳述完Smith的理論之後，我將論證兩件事：第一，關於直接實在論的辯護者所應完成的任務， Smith的討論其實涉及到兩個彼此獨立的課題，而他卻未能區分開來。第二，Smith的理論低估了所謂的「感覺與料感染」（the sense-datum infection）的影響。這兩項論點的結果是：即使Smith對於知覺意向性的解釋是正確的，他對於直接實在論的辯護仍是失敗的。我認為：單憑對於知覺現象（perceptual phenomenology）的理解，無法使直接實在論免於威脅；光是考慮如何抵擋「感覺與料推論」，並不足以反駁錯覺論證。直接實在論的支持者還必須設法回應「感覺與料感染」才行。本文最後會對此提供初步的建議。

I discuss the so-called “problem of perception” in relation to the Argument from Illusion: Can we directly perceive the external world? According to Direct Realism, perception provides direct and immediate awareness of reality. But the Argument from Illusion threatens to undermine the possibility of direct perception of the world. In The Problem of Perception (2002), A. D. Smith proposes a novel defense of Direct Realism based on a careful study of perceptual phenomenology. According to his theory, the intentionality of perception is explained in terms of three phenomenological features of perception: phenomenal three-dimensional spatiality, movement, and the Anstoss. He argues that this account of perceptual intentionality can resist a central premise of the Argument from Illusion, i.e. the “sense-datum inference.” After presenting Smith’s theory, I argue that he fails to distinguish two independent tasks for the direct realist, and that he underestimates the threat of the so-called “sense-datum infection.” My contention is that even if Smith’s theory of perceptual intentionality is correct, Direct Realism has not been saved from the Argument from Illusion. To resist the Argument from Illusion, it is not enough to merely consider how to block the sense-datum inference. The direct realist must also find a way to undermine the sense-datum infection. If so, I suggest, Direct Realism cannot be defended by perceptual phenomenology alone.