The four temperamental genera, which are the great matrices of personality, are the choleric, the sanguine, the phlegmatic and the melancholic. A genus is not a complete species, nor a closed description of the concrete person. It is a natural capacity that makes one matter of human action salient, met by an operation of its own; and that is why each genus occupies a pole on the two axes we have just seen, and not the other way around. The order of reading matters: first the matter and the operation, then the position on the axes, and only then the symbolic image that condenses them.
The choleric is the genus of the arduous. Its operation is action, that is, the impact capable of changing a resistance, and the method pictures it as dryness and electricity: sharp outline, direction, discharge. The choleric lives the world in a more direct and decisive way, more turned toward intervention, and their soul tends to ask: is there something I can do about this?
The sanguine is the genus of the pleasant. Its operation is expansion, that is, opening the pleasant to presence and participation, and the method pictures it as warmth and the radiance of the sun. The sanguine lives the world as a space of exchange, encounter and welcome, and their soul tends to ask: what is there here that is good, interesting or worth sharing?
The phlegmatic is the genus of transition, the passage from one state to another. Its operation is stability, that is, sustaining a configuration through time, including an activity already under way, and the method pictures it as moisture and plant life. The phlegmatic lives the world as something in which continuity has to be kept and one has to last, and their soul feels, before anything else, how much it costs to change state.
The melancholic is the genus of measure. Its operation is restraint, that is, the delimitation by criterion that holds, distinguishes and gives form to experience, and the method pictures it as cold and the crystallization of ice. The melancholic lives the world as something serious, demanding and charged with meaning, and their soul tends to ask: does this correspond to what it should correspond to?
The four genera are indispensable because they show that personality is not made of endless chaotic variations but of intelligible forms. The method, however, does not stop at them, because they are still too broad: they show the basic universes, but they do not exhaust the concrete form in which personality appears in a real person. Even so, without the genera nothing can be understood, because they are the method's fundamental language. They are what explain why some people get moving quickly and others feel more the cost of changing, why some renew themselves outward and others hold back inward, why certain temptations pass through power, others through reception, others through stability and others through the yardstick, and why certain natural goods appear more easily in one universe than in another.
In the created order, each genus is a capacity for natural virtue, that is, an aptitude for the matter of a cardinal virtue, without possession of it. The choleric has an aptitude for the matter of fortitude, the sanguine for that of temperance, the phlegmatic for that of prudence and the melancholic for that of justice. The correspondence, however, is not symmetrical. In the choleric, ease before the arduous can help fortitude and, at the same time, hide the fact that they have not yet learned to endure. In the sanguine, the taste for the pleasant makes temperance more necessary and more difficult. In the phlegmatic, waiting can serve deliberation and can also block its command. In the melancholic, comparison can serve what is due or distort it. The matter is the field in which each will be tested most, not the virtue already won.
In the fallen order, each of these goods can be egoized, that is, come to function as the condition of a thesis about one's own self. The choleric no longer wants only to act well; they need reality to confirm their power, and that way they arrive at pride. The sanguine no longer wants only to take part; they need to keep being well received, and that way they arrive at vanity. The phlegmatic no longer wants only to preserve what has value; they let the cost of moving define what they ought to do, and that way they arrive at lukewarmness. The melancholic no longer wants only to measure truthfully; they need the measure to preserve their position, and that way they arrive at envy. Each genus, then, is more than a personality style: it is a moral drama in potency, and it must be understood at once as a created capacity, as a structural form, as a field of temptation and as its own path to maturity.
It is precisely because these four worlds are real that it makes sense to speak, next, of their pure and mixed species. The genera are the ground, and the species are the concrete forms through which that ground takes on a face in a person, who may be you, your spouse or your child.