Aristotle takes a curious position on whether the sense of touch involves a medium.  It seems easier, simpler, and more intuitive to believe that there is no medium, and that the sense of touch works by having the sense object affect the flesh directly.  However, Aristotle imagines several thought experiments, which serve as arguments to bolster his position, all of which are clever, but which have been found wanting by some commentators. (1)  These arguments are laid out in De Anima II.11, the chapter which particularly explores and describes the sense of touch. 

The first of these arguments is the “Membrane Argument.”  We are told by Aristotle to imagine a membrane, stretched as an extremely thin layer around our body, or perhaps limited, for clarity, to only around a hand.  In such a situation, the membrane, “would communicate the sensation in the same way, immediately when touched”  (trans. Shields, 423a3-4).  We would not, Aristotle insists, think that the membrane was an organ, even though there was an immediate transmission of the perception.  So, just as an immediate communication does not suffice to make an organ out of a membrane, so too immediate communication of the perception in the case of the flesh does not make it an organ either. 

There is a modification of this argument, acknowledging the possible objection that the membrane example is rigged in favor of Aristotle’s conclusion: a membrane is not living, and so this example is doomed to failure from the outset, because all organs are necessarily living.  Coming immediately on the heels of the membrane argument, then, Aristotle offers up the “Natural Membrane Argument.”  The idea here is to imagine, however this would come about, that the membrane from the first example is now “naturally attached” (symphues) to the skin, rather than an artificial add-on.  Aristotle says that in this scenario, “the perception would pass through it still more quickly” (Trans. Shields, 423a5).  It is unclear how perception would occur more quickly than the instantaneity implied in the case of the mere membrane, but that it occurs, seems for Aristotle to result from the idea that some things, namely naturally affixed ones, are better media than others. 

Continuing on with this same line of thought, Aristotle next fleshes out his naturally attached argument by inventively offering air as that thing to which we become naturally affixed.  Supposing that were air to become naturally affixed to us, we would then think that sound, smell and sight were brought about by one thing, namely the air as our single organ (since they, of course, operate via air).  We would nevertheless be mistaken, as the organs would properly be the ears, eyes and nose.  So just as in the hypothetical case of air becoming naturally affixed to us, with air as a medium which appears to us as an organ, so too in reality in the case of flesh, where flesh is actually a medium but also falsely appears to us as an organ.  One important feature to pick up on here is that it is not the relative proximity of the object of perception that determines whether a medium is mistaken for an organ, but it is rather how indistinguishable the medium is from the sense faculty itself, in other words, how closely aligned the medium and faculty are.  This may in fact be only hard to distinguish because of our point of view, in that the sense of touch is in some way internal to flesh, and thus difficult to experientially separate from the medium of flesh.  In the same way that in the example of air becoming naturally fused to our flesh we would have difficulty in determining whether, for example, the air was the medium or the organ of hearing (when it fact the ear was the organ all along,) so it is the case now when we are with great difficulty trying to determine the difference between the medium and organ when it comes to flesh in the case of touch. 

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(1) In fact many consider these arguments poor.  But I do think, along with Polansky, that these arguments were attempting to make room for “the possibility for the flesh to be medium rather than sense organ”  (Polanksy 2007: 325)

Aristotle, and Christopher Shields. Aristotle De Anima. Trans. Christopher Shields. Oxford Univ Press, 2016.

Polansky, Ronald. 2007. Aristotle’s De anima. Cambridge: Cambridge University Press.