Distinction: The Deception of the Senses and Descartes' Error

Distinctions are important and dangerous. They can endlessly multiply arguments, but they can also help discover and preserve truth. An example of a culturally-ubiquitous lack of distinction-leading-to-error is in order.

I came across a video today (one of many I've seen from the past; I hear people carelessly making the same claim frequently):

Source: BuzzFeedVideo, "Proof Your Senses Are Lying To You," YouTube, October 12, 2013, accessed October 18, 2013, http://www.youtube.com/watch?v=nwV1xJu8qqM

Descartes made many errors. There's one I want to focus on here, and it persists through the tradition of modern philosophy and into popular culture today. It's the belief that our "senses deceive us" or even can deceive us. What's going on here, really, is an ambiguous use of the word "senses," and Descartes even makes the distinction between what our senses in themselves report to our mind and the judgments that our minds make of those sensory reports:

When the wax is in front of us, we say that we see it, not that we judge it to be there from its colour or shape; and this might make me think that knowledge of the wax comes from what the eye sees rather than from the perception of the mind alone. But this is clearly wrong, as the following example shows. If I look out of the window and see men crossing the square, as I have just done, I say that I see the men themselves, just as I say that I see the wax; yet do I see any more than hats and coats that could conceal robots? I judge that they are men.

Source: René Descartes, Meditations on First Philosophy, Marxists, accessed October 18, 2013, http://www.marxists.org/reference/archive/descartes/1639/meditations.htm, "Second Meditation: The nature of the human mind, and how it is better known than the body,"

Nevertheless, Descartes continues to insist that it is our senses that deceive us, and they are trustworthy only because of the goodness of God:

Thus I see plainly that the certainty and truth of all knowledge depends strictly on my awareness of the true God.

Source: Ibid., "Fifth Meditation."

Nevertheless, to be fair, Descartes seems to mean that we cannot derive clear and certain knowledge of things from the senses, not necessarily that sensory data itself is deceiving, but even here, Descartes is unclear, lacking in making distinctions, or at least not applying them consistently; for example:

God has given me no way of recognizing any such ‘higher form’ source for these ideas; on the contrary, he has strongly inclined me to believe that bodies produce them. So if the ideas were transmitted from a source other than corporeal things, God would be a deceiver; and he is not. So bodies exist. They may not all correspond exactly with my sensory intake of them, for much of what comes in through the senses is obscure and confused.

Source: Ibid., "Sixth Meditation." 

At various points—since I don't have the works in front of me, I can't verify exactly where—I've noticed that so many other modern philosophers have made similar claims as Descartes, namely, that the senses deceive and are untrustworthy. It's a claim that popular culture now takes for granted. Yet hardly ever is the distinction made between our sensory percepts and the judgments we form of those percepts. Error is found in a concrete judgment, a proposition that a thing is either so or not. Deception requires firstly the possibility of an affirmation or negation, not a brute datum, such as sensory stimuli. I am deceived about my judgment of a matter of fact, not the reality that the fact apparently reports.

Our senses tell us exactly what they tell us. Yes, that's a tautology and one of many factors that gives rise to the possibility for judgments and hence also truth and deception. Even people with "malfunctioning" sensory organs receive precisely what those organs communicate, but what the person judges of that sensory data is where deception can occur.