Prof Jung:

Well, there is something in the idea that people who are too metaphysical are bothered by their bodies.

For the more the mentality or the psyche leaves the body to itself, the more the body goes wrong.

The two ought to live together.

That explains the bad state of health of intuitive people who don’t even need to be metaphysical; it is enough that they are a bit too intuitive.

They live too much in mere possibilities, and then the digestion begins to suffer, they get chronic diseases, ulcers of the stomach or the duodenum, for instance.

Or they may get other disturbances of the body of an infectious nature; many organic diseases are due to this peculiar lack of attention.

People who have lived too much upon spiritual ideas should bring their attention back to their bodies.

So one can say it is always a wise thing when you discover a new metaphysical truth, or find an answer to a metaphysical problem, to try it out for a month or so, whether it upsets your stomach or not; if it does, you can always be sure it is wrong.

It is necessary to have metaphysical ideas-we cannot do without them-but it is also necessary to submit them very seriously to the test whether they agree with the human being: a good metaphysical idea does not spoil one’s stomach.

For instance, if I hold a metaphysical conviction that we live on after death for fifty thousand years instead of fifty million-if that is a solution-! try what it means if I believe in fifty thousand years only; perhaps that is good for my digestion-or bad.

You see, I have no other criterion. Of course, it sounds funny, but I start from the conviction that man has also a living body and if something is true for one side, it must be true for the other.

For what is the body?

The body is merely the visibility of the soul, the psyche; and the soul is the psychological experience of the body.

So it is really one and the same thing.

Therefore, a good truth must be true for the whole system, not only for half of it.

According to my imagination, something seems to be good-it fits in with my imagination-but it proves to be entirely wrong for my body.

And something might apparently be quite nice for the body, but it is very bad for the experience of the soul, and in that case I have a metaphysical enteritis.

So I must be careful to bring the two systems together; the only criterion is that both are balanced.

When life flows, then I can say it is probably all right, but if I get upset I know something must be wrong, out of order at least.

Therefore, people with one-sided convictions of a decidedly spiritual nature are forced by the body to pay attention to it.

I have seen many people who suffered from all sorts of ailments of the body simply on account of wrong convictions.

But it is a sickly thing to them, and gladly would they get out of their skin. Therefore hearken they to the preachers of death, and themselves preach backworlds.

Hearken rather, my brethren, to the voice of the healthy body; it is a more upright and pure voice.

More uprightly and purely speaketh the healthy body, perfect and square built; and it speaketh of the meaning of the earth.

Here you have it.

He trusts to the reaction of the healthy body.

The healthy body is the healthy life, and the healthy life is the life of the soul of man as much as his body, because soul and body are not two things.

They are one. ~Carl Jung, Zarathustra Seminar, Pages 354-355.