在路易斯（C.I. Lewis）的知識論中，感知（qualia）被視為直接的直覺及與生俱來的察覺。他非常明確的區分感知及布洛得（C.D. Broad）和羅素（Bertrand Russell）所認為的感覺材料（Sensa或sense-data）。對於布洛得和羅素顯然容許的「未感覺到」、「未完全感覺到」，或「不正確感覺到」之感覺材料（Sense-data）的可能性，路易斯卻視感知（qualia）為必定會被感覺到、且不可能感覺錯的。他認為布洛得－羅素的觀點不可思議，並說如此解說感覺材料是荒謬的。　　我論證布洛得－羅素的觀點至少是與路易斯的同樣合理。事實上，要適切的描繪及解說心理現象，去區分意識的現象層面（phenomenal aspect of consciousness）和意識的進入使用功能（accessing function of consciousness）或許是需要的。在論證此區分的合理性中，我援用了認知科學及現象學的研究。我還論證原則上，由實驗而得的證據可以決定布洛得－羅素和路易斯的觀點何者正確。在結論部分，我提出了這一觀點對路易斯的知識論發展之影響的看法。

n C. I. Lewis`s epistemology, qualia are taken to be directly intuited and inherently recognizable. He distinguishes sharply between qualia and that which C. D. Broad and Bertrand Russell refer to as "sensa" or "sense-data." Where Broad and Russell appear to allow for the possibility of unsensed, incompletely sensed, or inaccurately sensed sensa, Lewis regards qualia as given-to be is to be sensed and certain. Lewis finds the Broad-Russell view to be incredible and says of sensa so construed that they are "neither fish, flesh, nor good red herring." I argue that the Broad-Russell view is at least as plausible as Lewis`s and, indeed, that to adequately describe and explain mental phenomena, it may be necessary to distinguish the phenomenal aspect of consciousness (sensa or qualia) from the accessing function of consciousness. In arguing the plausibility of this distinction, I draw upon work from both cognitive science and phenomenology. I also argue that, in principle, experimental evidence could be adduced to decide the issue between the Broad-Russell and the Lewis views. In a concluding section I suggest implications of the view developed here for Lewis`s epistemology.