What is Desire?

106. What is Desire?

The Passion of Desire is characterized by the will to obtain some good or to avoid some evil. This promptly sends the spirits from the brain to all parts of the body that can perform the necessary actions for this purpose.

Particularly, they go towards the heart and the parts that supply it with the most blood. By receiving more blood than usual, it sends more spirits to the brain, both:

• to sustain and strengthen the idea of this will
• to pass from there into all the sensory organs and all the muscles that can be employed to obtain what is desired.

107. What is the cause of these movements in Love

There is such a connection between our soul and our body, that once we have linked some physical action with a thought, one of them does not present itself to us afterward without the other also presenting itself.

As seen in those who have taken some drink with great aversion while sick, they cannot drink or eat anything afterward that tastes similar without feeling the same aversion again; likewise, they cannot think of the aversion to medicines without the same taste coming back to their mind.

The first passions our soul had, when it first began to be joined to our body, must have been that sometimes the blood or other juice entering the heart was a more suitable nourishment than usual to maintain the heat which is the principle of life.

This caused the soul to willfully join this nourishment to itself, that is, to love it.

At the same time, the spirits flowed from the brain to the muscles, which could press or agitate the parts from which it had come to the heart, to make them send more of it.

These parts were the stomach and intestines, whose agitation increases appetite, or else also the liver and lungs, which the diaphragm muscles can press.

Therefore, this same movement of the spirits has always accompanied the passion of Love.

108. In Hatred

Sometimes, on the contrary, some foreign juice enters the heart. This juice is not suitable to maintain the heat, and even could extinguish it.

This causes the spirits rising from the heart to the brain to excite Hatred in the soul.

At the same time, these spirits also go from the brain to the nerves.

To prevent this harmful juice from entering the heart, these spirits push the blood from the spleen and small veins of the liver. These push this same juice back to the intestines and stomach, or sometimes force the stomach to vomit it.

Hence these same movements usually accompany Hatred.

The liver has many veins or conduits, large enough for the juice of the food to pass from the portal vein to the vena cava, and from there to the heart, without stopping at the liver.

But there are also an infinite number of smaller ones where it can stop. These veins always contain reserve blood, as does the spleen.

This blood is coarser than that in other parts of the body. They can better serve as nourishment for the fire in the heart when the stomach and intestines fail to provide it.

109. In Joy

At the beginning of our life, the blood contained in the veins:

• was sufficient nourishment to maintain the heart’s heat
• was so much that it did not need to draw any nourishment from elsewhere.

This excited in the soul the Passion of Joy.

At the same time, it caused the openings of the heart to open more than usual.

The spirits flowing abundantly from the brain, not only into the nerves that open these openings, but also generally into all the others that push the blood from the veins to the heart, prevented any new blood from coming from the liver, spleen, intestines, and stomach. That is why these same movements accompany Joy.

110. In Sadness

On the contrary, it sometimes happened that the body lacked nourishment. This must have made the soul feel its first Sadness, at least the one not joined with Hatred.

This also caused the openings of the heart to narrow because they received little blood; and a significant part of this blood came from the spleen, as it is the last reservoir that serves to supply the heart when it does not receive enough from elsewhere.

That is why the movements of the spirits and nerves that serve to narrow the openings of the heart and to lead blood from the spleen always accompany Sadness.

111. Desire

All the first Desires that the soul could have had, when it was newly joined to the body, were to receive things suitable for it and to repel those that were harmful.

It was for these same effects that the spirits began to move all the muscles and all the sensory organs in all the ways they could move them.

That is why now, when the soul desires something, the whole body becomes more agile and more disposed to move than it usually is without it.

When it happens otherwise that the body is so disposed, this makes the soul’s desires stronger and more ardent.

122. What are the external signs of these Passions?

What I have put here makes the cause of the differences in the pulse and all the other properties I have attributed to these passions above quite clear, without needing to explain them further.

But because I have only noted in each what can be observed when it is alone, and which helps to understand the movements of blood and spirits that produce them, I still need to address several external signs that usually accompany them and that are better noticed when they are mixed together, as they often are, than when they are separate.

The main signs are the actions of the eyes and face, changes in color, tremors, languor, fainting, laughter, tears, groans, and sighs.