What really distinguishes plants and animals?


It used to be said by the Philosophers that plants and animals share in common the powers of growth, nutrition and reproduction, but differ in that animals possess sensation whereas plants lack sensation. However, according to recent studies, plants also possess sensation but merely lack the animal organs, and so are slower to perceive.

So my question is, what powers/faculties really distinguish plants and animals?


Cell walls? Are there any plants that don’t have cell walls? Are there any animals that do?


What powers/faculties distinguish the two? The form/structure of their bodies is a given.


I think the burden lies first on why we’d need to philosophically distinguish them at all. Personally, I don’t see any reason to.


Ah, sorry. Didn’t realize I was in the philosophy thread. :stuck_out_tongue:


Some biologists claim it is movement, although this may need to be qualified because plants can move to a limited degree. In my opinion, the fundamental purpose of the brain is movement. All other brain functions, e.g., perception, cognition, communication, and reasoning, are biological adaptations in the service of movement. Not all animals have brains, though. Some animals control movement through neural networks of other topologies.


Bump. Any other answers?


Well, most animals have brains, but there are notable exceptions, like jellyfish. The general definition, which works almost all the time, is that plants produce their own energy (food) through complex chemical reactions like photosynthesis, whereas animals have to ingest food. It’s not perfect, because there’s always going to be the weird outlier, and of course, those features are not limited to plants or animals, so a sharper definition is that plants are eukaryotes who produce their own food, whereas animals are eukaryotes who have to ingest food, because there are prokaryotes and archaea who can also do these things (in fact, it’s now generally accepted that chloroplasts found in most plant cells originally cyanobacteria that were absorbed by very early plant cells, much as mitochondria were originally bacteria absorbed by early animal cells).


Thanks for the replies. I know I’ve always had trouble distinguishing a tiger from a tiger lily.:laughing:


Plants also have mitochondria.


At the most fundamental level, sensation and signaling are chemical processes, so there may not be a clean separation between plants and animals on that basis. Higher animals have sensation which is transmitted by nerves, which is relatively fast but still only a chain of chemical processes. Plants respond to stimuli and stress by different chains of chemical process which happen to be slower. Some people would call it signaling rather than sensation, but the distinction is somewhat arbitrary.

You may need to distinguish between sensation and perception. Without looking up the definitions, I believe sensation is the gathering of information, while perception involves classification or interpretation of that information, which in vertebrates takes place mainly in the brain.


Just a reminder


According to the Philosophers, the five external senses are: sight, hearing, touch, taste & smell.

Whereas the five internal senses are: memory, recollection, imagination, estimation & common sense.

Which of these do you believe plants would possess?


We can very clearly see animals react to stimuli while we most often need special equipment to recognize it in plants.


Yes, even though this is the philosophy section. As long as it doesn’t have to do with Catholic theology: who cares? why does it matter?

I’m sure questions like these mattered to those you admire such as Thomas Aquinas and Albert the Great. Not even being sarcastic.


There are exceptions like the Venus Fly Trap, which closes its trap in less than one second when triggered.

(At this link a short video is available for free, but not the full video.)


The correspondence, when one exists, is at a basic physical level. Plants respond to light, but it is not like our sense of sight. Plants respond to (and even communicate by) chemical signals in the air, but it is not like our sense of smell. Some plants are touch-sensitive. Plants probably detect (taste) nutrients and water in the soil and seek them with their roots.

I cannot think of any plant analog to the five internal senses.


You know what Thomas a Kempis said. :stuck_out_tongue:

Oh to be one of those to whom truth communicates itself directly-- not by means of symbols and words, whose meaning changes with time, but in its very nature! Our own estimate, our own way of looking at things, is always putting us in the wrong, by taking the short view. And here we are, splitting hairs about all sorts of mysterious problems which do not concern us-- we shall not be blamed, at our judgement, for having failed to solve them. Strange creatures that we are, we forget the questions which really matter to us, matter vitally, and concentrate, of set purpose, on what is mere curiosity and waste of time. So clear-sighted are we, and so blind!

Why should we be concerned to divide up things into “classes” and “families”? We get away from all this tangle of guess-work, when once the Eternal Word speaks to us. From him alone all creation takes its origin, and thereofre all creation has but one voice for us; he, who is its origin, is also its interpreter. Without him, nobody can understand it, or form a true judgement about it. Until all things become One for you, traced to One source and seen in One act of vision, you cannot find anchorage for the heart, or rest calmly in God…

The point that was being made was that you’re looking at a classification system that was designed to classify physical objects, and are trying to philosophize it. I can create any classification system I want-- the Dewey Decimal system or the LCC or the Universal Decimal System or something homegrown. So just like Dewey Decimal can categorize things out to the third or fourth decimal, if desired, it doesn’t take into account whether a book is red, or is over 500 pages, or whether it was printed in 1995, whether it makes me cry, or whether it sold over a million copies.

So, the same thing is true with plants. The idea of the “plant kingdom” was founded on physical characteristics. The first one is having a cell wall— which is why you have a Fungi Kingdom, because fungi aren’t categorized as plants, which is why algae isn’t a plant. Second, plants have cuticles. And third, plants make their own food-- even if they may supplement it eating other organisms, like a Venus flytrap, which has photosynthesis, but also eats insects.

Things like discovering how plants communicate with each other is still a baby science. There’s a ton we don’t know.

So until you have the ability to fully know the powers and faculties of all plants and all animals, it’s just a sort of speculative exercise… which is okay for philosophy… but you’re ultimately trying to make a classification system that was designed to account for X also take into account Y… which we have incomplete information about.


I don’t even know what you’re referring to. I acknowledged that plants have senses and didn’t attempt to dispute this. I asked what powers/faculties really distinguish plants and animals. You asserted that the answer is not black and white but grey, however you did not elaborate.

For the same reason why I think studying/contemplating God’s creation is important in general.


Perhaps you and Aristotle mean different things by “sensation”.

For example, commentary on Aristotle’s “De anima” by St. Thomas Aquinas (https://dhspriory.org/thomas/DeAnima.htm#32): “This answer is required by the fact that colour has two modes of being: a material mode in the object, a spiritual mode in sensation.”. Presumably, merely reacting to the environment is not sufficient for “sensation”.

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