..I am hoping that someone can help correct me if I am wrong or mislead.

Using a tree as an example to explain my question: it is difficult to narrow down an exact definition of a tree because every tree is different. So to define a tree, we are actually defining everything else as not a tree, until we decide it fits into the tree category. ..So if I had a set of copper wire, I would say that it is not a tree. But if I fold the wire into the shape of a tree, now it can be recognized under the definition of a tree.

Is this a correct idea that I am portraying or am I off?

  • 1
    I do not think a set of copper wires, however shaped, should fall under a definition of a tree, you probably just mean a tree shape. And loose colloquial terms like that neither have nor need exact or "true" definitions. Their vagueness is part of their usefulness, they can be used flexibly with context making up for the vagueness. When there is a need for something more precise it does not have to capture all the colloquial uses of the word, only those relevant to the task, see e.g. the mathematical definition of "tree" in graph theory.
    – Conifold
    Oct 19, 2019 at 9:13
  • 2
    Hello, I'd suggest introducing some philosophical terminology: Apparently, your question asks whether concept building starts purely negatively, ie. with a general "thing" which is distinctive, but only determined insofar it is not like other determinate things. Then, it gradually becomes more determinate by realising positive properties that form the actual concept of that thing. This way, the more philosophically inclined readers will immediately get what you are suggesting. Correct me if I got this wrong, or, if not, please rephrase the question accordingly.
    – Philip Klöcking
    Oct 19, 2019 at 9:16
  • 1
    @Conifold does "not think a set of copper wires, however shaped, should fall under a definition of a tree". Spanning Tree Protocol - Wikipedia would disagree. Oct 19, 2019 at 12:25
  • 2
    We do not define an object, i.e. an individual tree, but a concept. Oct 19, 2019 at 12:31
  • 1
    @RayButterworth Spanning tree is a tree subgraph containing all vertices of a graph. Aside from the shape, it has little to do with the colloquial "tree".
    – Conifold
    Oct 19, 2019 at 12:36

3 Answers 3


The definition you're suggesting would be circular.

So to define a tree, we are actually defining everything else as not a tree

Of course, to define everything else as 'not a tree' you would first need to a have conception of 'tree'. Also, notice how you say "everything else", which presumably means "everything that's not a tree". So we define everything that's not a tree as 'not a tree'. Sounds about right, but it's not informative at all. To someone who doesn't know the meaning of 'tree' such a definition would be of no use.

  • I'm trying to upvote this but im logged in as a guest, my first question. the last sentence you wrote is helpful for me
    – Noah
    Oct 19, 2019 at 19:18

[I]t is difficult to narrow down an exact definition of a tree because every tree is different. So to define a tree, we are actually defining everything else as not a tree, until we decide it fits into the tree category.

Welcome to SE Philosophy! This is a very philosophical question, and one that hinges on the nature of definition. In your title you use the phrase "true definition", and I think I speak for many who would say that there is no such thing as a "true" definition if you mean the phrase to mean universal, beyond argument, so on. Most definitions are used by convention, which is to say there is a general agreement and use, but no authority. You have some options:

Use a soft dictionary like Webster's or the OED. These definitions are generally simple and agreeable to most people. Another place you might find a definition is among biologists, particular botanists who study trees. Believe it or not, not all living organisms fit into the neater categories of biologists devise and they might argue over the definition of an organism.

But this is a question over what a definition really is, and that's where philosophy steps in! For instance, definitions, broadly speaking are intensional and extensional. What you are doing is trying to capture the essence of the tree by speaking to what it means (semantics) to be a tree. Another way would be to point to all trees or list all of the particular members of the set of trees, which is considered extensional. Having so many different kinds of definitions might be confusing, and there are more types, like the operational definition!

So, to answer your question specifically, to some extent, people must agree to a definition of a tree before attempting to use the term. To complicate matters, the famous philosopher Ludwig Wittgenstein anticipated findings in cognitive science which show that sometimes our brains define members of a category even if they have no properties in common at all! Wittgenstein noticed a category like "game" has members who share "family resemblances" but have no properties exactly in common. This has been validated by the linguist Elanor Rosch who showed our brains build prototypes to categorize concepts.

A related term in philosophy is that of natural kinds whose own definition is controversial among philosophers showing that not only do philosophers disagree over definitions, but disagree over the definition of definitions!

Notice on the comments of your question, the question of what a "tree" is depends on whether you're a biologist and study those trees or a computer scientist studying trees. Why use both? Because our brains work with conceptual metaphors.

Like most questions in philosophy, your question can only be satisfied, and not necessarily answered with absolute authority. That's why questions like yours tend to just raise more questions! (What does 'is' mean when one says "That is a tree"? Or how do we know for sure that we agree when we claim to be a tree is truly a tree?

  • Whe we define something must the definition corresponds to physical objects? Are the definitions abstractions? I mean can we define something e.g. "flying crocodile=a crocodile that flies" irrespective of the fact that such object doesn't exist in real world? Also in the category "flying crocodiles" would go only the objects of our world that meet the criteria of the definitions? Because when we think about an object e.g. car, house etc we can also imagine other worlds with such objects. So can these objects (cars,houses) of the other worlds fit into the category of cars?
    – ado sar
    Jul 30, 2020 at 23:27
  • @adosar One generally can make a definition of anything one likes, however, the great philosophers then arrive at the question of is it meaningful and real? Whether or not something is real depends on your metaphysical views about correspondence theory of truth and https://en.wikipedia.org/wiki/Coherence_theory_of_truth, among other theories. Russell, Quine, and others have their respective takes on these sorts of issues.
    – J D
    Aug 2, 2020 at 22:03

Words change over time. If looking for any ‘true definition’ if it exists, it is buried in prehistory (before the age of writing) and so etymologies going back to prehistory can only be speculative. The word at the origin of the meaning ‘tree’ (the plant), may have come from the same prehistoric ancestor of the Latin word ‘terra’ and French ‘terre’ (which mean the ‘earth’). In Dutch and German words for a tree do not resemble English tree and neither does it relate to a prehistoric meaning of the word ‘earth’. German ‘Baum’ and Dutch ‘boom’ both meaning tree relate to English ‘beam’. So it seems that the ‘true definition of a tree in prehistory was a ‘beam from the earth’. This is why the Axis Mundi in mythology is sometimes symbolised as a tree. I am researching the ‘true definition’ of words in prehistory. And we see a parallel with animals. Animal has similarities in spelling with animation. So animal carries a meaning of movement because unlike a tree that is a beam, animals roam the earth. In Dutch and German the words for animals were not derived from movement (Bewegung/Beweging) but they are derived from the same ancestor-word as ‘terra’. German ‘Tier’ and Dutch ‘dier’ show that the Germannic words ‘animal Tier’ is descriptive for ‘animation (on the) earth’ unlike ‘beam (from the) earth’. The description is the observation of the main difference between animals and trees, because animals move and trees do not. Because in different languages the same word-offspring shows up with different meanings shows that a) the meanings for the words animal and tree are younger words than those words meaning movement and earth. And b) these words are in relation to each other and to common descriptive meanings. The answer can be that a word may not always contain the full ‘true’ (and I would here replace ‘true’ with ‘initial’) definition and may be rooted in a part of the initial definition, that as a phrase in itself (the words on their own) did not mean what we use it for now. It formed a description. Mind you, I know of no other scientific research int his direction, because the method I use is not commonly accepted by scholars, so consider this answer philosophical, suggesting an answer based on the term ‘true’ which I interpret as ‘initial’ regarding the definition of a word.

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