This post is about how Naturphilosophie, the natural science branch of German idealism, was expressed in systematics back in the first third of the 19th century. Reads those two links as background knowledge, if needed. The idealists (the natural scientists who followed Schelling and Oken‘s idealism) were also trying to classify organisms, the job wasn’t left only for the empiricists.
Oken was especially interested in this venture, as you can see in an original of his classic 1825 book Lehrbuch der Botanik that I vandalised and scanned (really!). The highlighted passage says that the ordering of plant relationships is reflected naturally in their development.
Similarly, when speaking of animals in his magnum opus, Allgemeine Naturgeschichte für alle Stände, he seeks to order animals on the basis of their physical characteristics, specifically saying that there are so many varying developmental stages and anatomies in animals that a complete classification with varying hierarchies is possible.
The reason I bring this up is because Oken is speaking of a natural system, not a synthetic classification – this is an important point, as this reflects exactly what we nowadays seek to do with our phylogenies, and is the ultimate goal of true systematics.
That said, these are German idealists we are talking about. Nowadays, we use cladograms and phylograms to graphically display our systems. The idealists had all sorts of ways. A prominent one, as shown above (from the French translation of C. G. Carus’s 1828 Grundzüge der vergleichenden Anatomie und Physiologie), is the use of concentric circles. This in fact replaces the ladder or scala naturae – remember that in these times, progressive evolution, with humans being the pinnacle of any system, was the rule.
The reason for circles, and other geometric shapes, lies in German idealistic values. When it came to mathematics, German idealists were almost Pythagorean in their admiration of the “mathematical order” of nature, and they viewed the circle with special reverence: to them, it was the shape from which all others can be derived. The same thinking was found in classical Antiquity. In this way, the idealists tied their search for natural systems with their mystical notions.
Of course, given the inherent vagueness of how idealists viewed the world, some authors chose other symbolisms for representing their systems. Kaupp used pentagrams, since humans have five senses. Yeah, really. More imaginative was Goldfuss, who used an egg form, with the various groupings in concentric circles and ovals within the egg.
This obsession with mathematics is typical of German idealism, as maths was perceived as the only way to understand the true nature of a system. This reached quite a sophisticated level with Ludwig Reichenbach’s suggestion that animals and plants can be classified according to their shapes, and with some algebra, we can elucidate which are the most derived by calculation – in other words, a form of phenetics.
Combined with their very idealised diagrams, this very mathematical view of things led to very rigid systems. Whatever is in a circle cannot migrate out, or else the circle is distorted – that destroys the geometry, and since nature is perfect, we can’t have that. This is why German idealism failed, at least from the point of view of systematics. It is clear that some organisms would not fit into neat little circles; these had to then be accomodated as transitional forms between one circle and the other. All this just to avoid breaking the supposed harmony of nature.
We may look at this now and laugh, but I, for one, find it fascinating. German idealism is all but dead now, along with Romanticism. But it’s quite entertaining to wonder how these kinds of diagrams would be used today to represent the kind of systems we have today, which would include stem-group taxa. Each circle would represent a total-group; any division between stem- and crown-group would be impossible to show, as far as I can see.