在近數十年來，有關亞里斯多德知覺理論的研究，環繞在一個關鍵爭議上。R. Sorabji認為，根據亞里斯多德，知覺乃是建立在某種「典型變化」的基礎上，亦即當我們在知覺時，知覺器官乃是如實地接受知覺形式、物理性地歷經的性質變動，例如在看到紅色時，我們的眼球也必須變成紅色。反之，M. Burnyeat則援引Aquinas的亞里斯多德知覺理論詮釋，認為知覺乃是一種純粹「精神性的變化」；這種精神性的變化，Burnyeat認為，與器官典型的性質變化一點關係都沒有，也無須底層的物理或材質變化為其生理基礎；因為我們當知覺時，知覺器官僅是覺察到知覺形式，而非物理上如實地接受它們。針對這個爭議，本文試圖採取一種折衷的詮釋立場。本文並不認為，知覺活動等同於或承載在知覺器官的典型性質變化之上。然而，本文亦不認為，知覺活動與器官之生理或物理變化絲毫無關，如Burnyeat所設想的那樣。延續近年來流行的「編碼說」的詮釋立場，本文嘗試論證，在知覺活動中，知覺器官雖未歷經典型的性質變化，但它仍然歷經某種材質性的變動，而知覺形式則正是被「編碼」在這種變動之中。然而，相較於近年流行的各種「編碼說」立場多半忽略了，被編碼的變動仍然是某種材質性或生理性的變動這個事實，也未注意到這個事實對亞里斯多德整體知覺理論乃是某種潛在的威脅，本文嘗試指出，亞里斯多德的「知覺作為中道」說法，恰好可解決這個困難。

In recent decades, scholarly researches on Aristotle's theory of perception focused on a central debate concerning the role which the physiological process plays in perception. On the one hand, R. Sorabji claimed that perceiving, on Aristotle's view, involves a physiological process in which the sense-organ literally takes on the perceptible quality of the object. That is, perception has the ＂standard alteration＂ (change of quality) of the sense-organ as its physiological basis. For example, when we see a red apple, the organ of sight (the eye-jelly) should be physically turning into red. In contrast, M. Burnyeat suggested that perception is purely a ＂spiritual change＂ (to use Aquinas' term), which has nothing to do with the standard alteration suggested by Sorabji. Moreover, Burnyeat insisted that there is definitely no physiological or material change taking place during perception, because perceiving, as a pure spiritual activity, does not require any underlying material process as its physiological basis. Hence, on Burnyeat's reading, the physiological process has no role to play in perception. This article attempts to find a proper balance between these two radically contrasting interpretations. First, I will show that there is no clear evidence in Aristotle's text to claim that the physiological process involved in perceiving is the organ's literally taking on the perceptible form, as Sorabji suggested. Second, I will prove that Burnyeat's position is not totally persuasive either. For it is not the case that perception has nothing to do with any physiological or material process taking place in the sense-organ. Following the interpreting line recently suggested by several structuralist approaches, I try to argue that although the sense-organ does not bear a standard change of quality during perception, it is nevertheless affected by an ＂encoded＂ movement induced by a likewise encoded movement of the medium. In this way, the sense-organ will receive only a coded message, without really exemplifying the perceived quality. However, since the organ's reception of the coded message is still supposed to be a physiological change, it would be very difficult to explain how perceiving can be grounded in such a process; for one of the main theses in Aristotle's theory of perception is that perceiving is an ＂activity＂ (energeia), which should not be constructed by any physiological or material change whatsoever underlying it. This dilemma, I think, can be evaded by appealing to a famous proverb in De Anima that ＂perception is a mean.＂