Taxonomy (Or Why Modern Biological Categories are Wrong)

cladeAristotle was the first to systematically lay out various living things in the world. According to him, they could be divided into three categories: plants, animals and rational beings (humans). Insofar as biology is concerned, human beings are animals. Therefore, there were two biological categories: plants and animals. Carl Linnaeus extended this knowledge to cover many new kinds of plants and animals, and created more divisions below that of plants and animals. Many of our modern biological categories come from him. The highest division was the kingdom and there were two kingdoms: plants and animals. In 1866, Ernst Haeckel suggested that simple single celled organisms form a third kingdom that he originally called Monera. (He later called this kingdom Protista.) His reasoning behind this change was that biological divisions show historical ancestry (common descent). Modern taxonomists have followed this new pattern and begun a program of categorizing biological things according to ancestry. This is wrong because it is contrary to the purpose of biological categorization.

There are thousands and thousands of different kinds of biological things. There are also many possible ways to categorize them. We might categorize living things by considering how we use them. So weeds refer to plants that we do not want, trees refer to large plants that provide shade, vegetables are edible plants with a similar kind of taste and fruits are plants that have sweet parts. This kind of categorization does not help us understand the living thing. It simply helps us categorize the living thing according to our purposes for it. In fact, any external categorization will not help us understand the living thing. I might name plants according to where they are found, whether I like them, where I bought them or what they can be used for. But these things may vary even if the plant (or animal) stays the same. Furthermore, even if these things do not vary, the explanation for why they do not vary includes knowledge not related to the living thing in question. For example, the reason why pineapples are edible partially has to do with the human digestive system. Finally, even the knowledge about the living thing itself does not unify our knowledge of that living thing. So no externally based categorization scheme is proper if our goal is understanding the living thing itself.

Categorizing living things by their ancestry is an external categorization scheme. The explanation why two living things were placed in the same category would be an external fact (that it is the best fit for those two individuals given the rest of biology). Although historical knowledge is invariant across researchers, it includes both facts about the living thing itself and facts about the rest of the living things that happen to live in the world. Secondly, knowing that dogs and wolves share a common ancestry does not unify our knowledge of dog or wolf biology. Knowing that both dogs and wolves are mammals (and that being mammalian is more fundamental than being a dog or a wolf), does unify our knowledge of either a dog or a wolf.

When we categorize living things we must begin with what is most fundamental, and work our way to what is least fundamental. What is most fundamental to a living thing is the reason why it is alive. Without that, it would not be a living thing at all. Everything else that a living thing does supports the life of that living thing first of all. Least fundamental are the parts of the living thing that can change without harm to that living thing – such as the length of hair, the color of hair or the growth of new branches. Nowhere in this scheme is there room for facts about the ancestry of living things.

The purpose of categorizing living things in biology is to organize them in order to understand them in themselves. The purpose requires categorizing living things according to differences in those living things beginning with the most fundamental differences. Since the differences between living things are purely internal, there is no room for history. Therefore, classification schemes such as cladistics that are based on historical relationships between organisms are universally wrong.

Essence and Existence

I have shown that there are two problems with universals and particulars. If there were a way to distinguish between individuals and universals, then there would be a solution to these problems. The distinction between an existence and an essence is such a thing. Each individual has a distinct existence but a universal has a common essence.

Universals are any thing that has a name. For example, redness, humanity and oneness are all universals. Each of these things are different from each other because of what they are. The name for “what it is” is essence. So the essence of redness is the color red, the essence of oneness is unity and the essence of humanity is rational animality. Each of these essences is different from each other, but every instance of an essence is the same essence.

Particulars are named with “this”, “that” or by pointing. So my apple is different from your apple, even if they have the same essence. This difference is their existence. That something is – that it exists – is normally different from what it is. Even though my apple and your apple are the same thing because they are both apples, they are different things because they have different existences. I can destroy my apple, and yours remains unharmed. The existence of my apple is not a feature of my apple. The existence of my apple just is my apple existing right now.

The previous problem with universals can now be resolved. The redness of a painting and a box are the same because they have the same essence. The redness of the painting is different from the redness of the box because each one has a different existence. What is true of redness is true of all universals, and all named things. Anything that is named, is unique as a particular because its existence is unique. It is the same universal because each instance of that universal has the same essence as any other instance.

The previous problem with particulars can also be resolved. There is no feature or history that makes one particular unique. So Stephen is not unique because he has a particular history, has a unique genetic code or because of any other feature. He is unique because his existence is different from absolutely everyone else’s existence. If he were to have an identical twin, then each one would have a different existence. That is the only thing that is different from every other thing that no other thing could ever share with him.

Since the previous problems with particulars and universals are solved, it is natural for further problems to arise. There are several areas to examine. One of them is various essences. Categorizing them and determining which is most fundamental – if any – is a next step. Another area is the difference between essence and existence. Particulars must have both, but how are they related to each other? A final area is the nature of existence itself.

I will begin with the categorization of essence. Next I will discuss different universals and the relationships between them.