Ed Feser: Plants Have No Qualia

Ed responds to a blog post of mine here.

In a seemingly common move by modern Aristotelians, he first plays the "but he doesn't really understand what we are saying" card. Well, no, Ed, I understood perfectly well that the issue was about qualia, about whether there is something it is like to be a plant.

That being cleared up, let's get down to the empirical issues that we might use to judge whether there is something it is like to be a plant. Here, I believe the key issue is that much of the activity of plants does not look like activity to us, so that only careful scientific investigation reveals how active they actually are. For instance, Ed says:

"Hence, imagine that dry grass could feel the oppressive heat of the sun or experience thirst and the craving for water. What would be the point? It would not be able to do anything about its circumstances and would thus, unlike an animal, suffer without being able even in principle to remedy the circumstances leading to that suffering."

This is simply false. Plants can and do do things about circumstances like these. For instance, the rhododendrons in my yard, in extreme heat, curl up their leaves, lessening water loss. Plants that undergo periodic dry spells develop deeper root systems than those that do not.

Ed contrasts plants with animals as follows:

"An animal is aware of various aspects of its environment for the sake of the motions toward or away from those aspects that that awareness makes possible, and feels drawn toward or repelled by those aspects as a consequence. Thus the absence of locomotive and appetitive powers in plants is evidence that awareness is absent as well, for awareness would be pointless in that case."

But, again, it is simply empirically false that plants do not move towards or away from aspects of their environments. They merely do so at a much slower rate than do animals, so it is not readily apparent that they are doing so. But it has been found that plants "recognize" others of their own species, actively work to drive off plants of other species, and respond to insect attacks with counter-attacks of their own.

The problem is not that I do not understand the Aristotelian argument for the lack of sentience in plants. The problem is that, by Aristotelian criteria, that judgment ought to be revised in the light of a large amount of recent research.


  1. The standard aristotelian account is that nutrition, growth and reproduction are the fundamental powers of all living thing, and that plant life in particular is limited to these. Which of the activities you have described require sensation (cognition and appetite) over and above these basic three powers?

    1. Driving off enemies? Moving to avoid hostile conditions? Moving towards beneficial conditions? I mean, these are the *exact* sort of things sensation is supposed to be "for" in animals, on the standard aristotelian account.

    2. Do they do these activities by means of heterogenous organs of sensation and in virtue of estimative judgments which move their sensitive appetites so that they seek pleasure or avoid pain? Or can these activities they display be accounted for by the nutritive and augmentative powers shared by all living things? If you can show that plants have distinct organs of sensation - some heterogenous part with a function that differs from the other parts of the plant, which is capable of making sensible qualities known to the plant, then I say you've got a case. Chemical changes in the plant in reaction to contact with airborne chemicals seems to be an insufficiently differentiated process to constitute sensation in the standard aristotelian account.

    3. Charles, I regard myself as a friend of A-T philosophers. I hope to stop you from repeating earlier mistakes.

      Here, was have some evidence that plants can hear sounds, *despite* not having distinctive sense organs for doing so. There are two possible A-T- responses:

      1) Aristotle / Aquinas / Authority X says this can't be, so we must interpret it some other way; or
      2) Aristotle / Aquinas / Authority X didn't understand that this was possible, so we must interpret *him* some other way.

      The Aristotelians in 1600 almost all took option one: let's stick with the ancient authorities, whatever the evidence points to. This resulted in A-T philosophy being out of the conversation for 400 years. Now, when you are just getting back in, I'm really just trying to help you guys not make the same mistake a second time.


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