The wheel is not a secondary visual aid or a pretty way of arranging names: it is the graphic expression of the method's architecture. It shows that the temperaments are not loose pieces but real positions in an ordered field of tensions, neighborhoods, passages and oppositions. If the axes reveal the structure of the system, the wheel shows that structure laid out, and lets you see at once what the previous chapters prepared: the four poles, the passages between them, the pure and mixed species, the oppositions and the unity of the whole.
The wheel exists because the temperaments are not related arbitrarily. There are real proximities and real oppositions; there are species that touch, others that modulate one another and others that contrast deeply. This arrangement in space is not a teaching diagram but a consequence of the method's structural logic.
Poles, passages and opposites
At the four cardinal points of the wheel stand the pure species (choleric, sanguine, phlegmatic and melancholic), which work as anchors. Around them, the mixed species appear as passages between neighboring universes: between the choleric and the sanguine arise the choleric-sanguine and the sanguine-choleric; between the sanguine and the phlegmatic, the sanguine-phlegmatic and the phlegmatic-sanguine; between the phlegmatic and the melancholic, the phlegmatic-melancholic and the melancholic-phlegmatic; and between the melancholic and the choleric, the melancholic-choleric and the choleric-melancholic. The mixed species, then, is born of the living border between two neighbors, and not of "anyone with anyone else." That is why the system has twelve species, and not an arbitrary number of combinations.
This becomes even clearer when you look at the opposites. On the wheel, the choleric and the phlegmatic occupy opposite poles of the same axis, and the same goes for the sanguine and the melancholic. These pairs do not mix into a species, and not by convention, but because opposites do not form a neighborhood: they pull on the system as contraries, not as continuity. The wheel thus shows three kinds of relation: neighborhood between nearby species, opposition between poles of the same axis and continuity in the passages between universes. Each species, then, is more than a name: it has a place, two immediate neighbors, a dominant universe, a greater or lesser distance from the others and an opposition that helps define its contrast.
The wheel as a reading tool
That is why the wheel helps so much in diagnosis. It prevents confusion between nearby species and sheds light on differences between species that, at first glance, might look the same. The choleric-sanguine and the sanguine-choleric are neighbors, but not identical; the phlegmatic-melancholic and the melancholic-phlegmatic are close, but cannot be mistaken for each other; the choleric-melancholic and the melancholic-choleric share the same border, but have different centers of gravity.
The wheel also reveals that each genus forms a universe of five positions: the pure species, the two mixed species in which it comes first and the two in which it comes second. The choleric universe, for example, includes the pure choleric, the choleric-melancholic, the choleric-sanguine, the melancholic-choleric and the sanguine-choleric. The sanguine universe includes the pure sanguine, the sanguine-choleric, the sanguine-phlegmatic, the choleric-sanguine and the phlegmatic-sanguine. The same holds for the other two, which shows that each genus is not an isolated block but a field of influence.
Finally, the wheel organizes the method's symbols. At the pure poles stand the lightning, the sun, the leaf and the ice. In the passages appear the closed circuit, the plasma, the fire, the sunflower, the daisy, the lichen, the snow and the magnetite. These symbols tell the shape of the movement between the poles, and it is on the wheel that they become intelligible together. The system could be understood through concepts alone, but with the wheel it gains a body and a visible unity, and whoever has it before their eyes sees that the twelve temperaments are not useful descriptions piled together but expressions of an order that no one invented, only recognized.